CAIRO >> Security forces fired tear gas and clashed today with several thousand protesters in Cairo’s Tahrir Square in the third straight day of violence that has killed at least 24 people and has turned into the most sustained challenge yet to the rule of Egypt’s military.

Throughout the day, young activists demanding the military hand over power to a civilian government skirmished with black-clad police, hurling stones and firebombs and throwing back the tear gas canisters being fired by police into the square, which was the epicenter of the protest movement that ousted President Hosni Mubarak in February.

The night before saw an escalation of the fighting as police launched a heavy assault that tried and failed to clear protesters from the square. In a show of the ferocity of the assault, the death toll leaped from Sunday evening until this morning. A constant stream of injured protesters — bloodied from rubber bullets or overcome by gas — were brought into makeshift clinics set out on sidewalks around the square where volunteer doctors scrambled from patient to patient.

The eruption of violence, which began Saturday, reflects the frustration and confusion that has mired Egypt’s revolution since Mubarak fell and the military stepped in to take power.

It comes only a week before Egypt is to begin the first post-Mubarak parliamentary elections, which many have hoped would be a significant landmark in a transition to democracy.

Instead, the vote has been overshadowed by mounting anger at the ruling Supreme Council of the Armed Forces, which will continue to hold power even after the vote. Activists accuse the generals of acting increasingly in the same autocratic way as Mubarak’s regime and fear that they will dominate the coming government, just as they have the current interim one they appointed months ago.

The military says it will hand over power only after presidential elections, which it has vaguely said will be held in late 2012 or early 2013. The protesters are demanding an immediate move to civilian rule.

“What does it mean, transfer power in 2013? It means simply that he wants to hold on to his seat,” said a young protester, Mohammed Sayyed, referring to the head of the Supreme Council, Field Marshall Hussein Tantawi.

Sayyed held two rocks, ready to throw, as he took cover from tear gas in a side street off Tahrir. His head was bandaged from what he said was a rubber bullet that hit him earlier today.

“I will keep coming back until they kill me,” he said. “The people are frustrated. Nothing changed for the better.”

An Egyptian morgue official said the toll had climbed to 24 dead since the violence began Saturday — a jump from the toll of five dead around nightfall Sunday. The official spoke on condition of anonymity because he was not authorized to release the numbers. Hundreds have been injured, according to doctors in the square.

At the makeshift field clinics around Tahrir Square, medical volunteers rushed between injured protesters staggering in, or being carried in by comrades. Most of the clinics were simply a partitioned-off sections of sidewalk.

Mohammed Mustafa, a doctor at the main clinic set up inside a nearby mosque, said his site alone was treating an average of 80 cases an hour and that many of the wounded did not want to be taken to hospital because they feared arrest. He and other doctors said most of the injured had breathing and eye problems and wounds to the face from rubber bullets. A number of protesters have lost eyes from rubber bullet hits since Saturday.

During the overnight assault, police hit one of the field clinics with heavy barrages of tear gas, forcing the staff to flee, struggling to carry out the wounded. Some were moved to a nearby sidewalk outside a Hardees fast food restaurant. A video posted on social networking sites showed a soldier dragging the motionless body of a protester along the street and leaving him in a garbage-strewn section of Tahrir.

As the violence raged, the military council issued a long-awaited anti-graft law that bans anyone convicted of corruption from running for office or holding a government post.

The timing of the move suggested it was an attempt to placate protesters. But the law falls far short of demands by many that all members of Mubarak’s former ruling party be banned from politics.

The interim government also said today it was seeking to replace culture minister Emad Abu Ghazi, who submitted his resignation Sunday to protest the Cabinet’s response to Tahrir clashes, MENA reported.

Protesters also marched today other cities, including thousands of students in the coastal city of Alexandria. calling for those responsible for the violence in Cairo to be punished.

The protesters’ suspicions about the military were fed by a proposal issued by the military-appointed Cabinet last week that would shield the armed forces from any civilian oversight and give the generals veto power over legislation dealing with military affairs. It would also give them considerable power over the body that is to be created after the election to draft a new constitution.

At the same time, there are deep concerns the election will bring little democratic change. Many worry that stalwarts of Mubarak’s ruling party could win a significant number of seats in the next parliament because the military did not ban them from running for public office as requested by activists.

Many also believe that whoever wins the election, the military will continue to wield its domination over the next government. The current civilian government has been little more than a facade for the military, activists say. It has done little to bring about economic and political reform and has stood unable — or unwilling — to act as woes have mounted in Egypt.

Today, German Foreign Minister Guido Westerwelle called on Egypt’s rulers to listen to the protesters.

“Those in charge in Egypt would be well advised to take people’s political demands and justified concerns seriously and act fast to create the right environment for the upcoming elections,” Westerwelle said.

He called on all sides to refrain from violence so the upcoming election can be held in “a peaceful environment” and dispatched his Middle East envoy to Cairo.

Over recent months, security around the country has fallen apart, with increased crime, sectarian violence and tribal disputes. The economy has badly deteriorated. Because of the weekend violence, Egypt’s main stock index fell for a second straight day Monday, and airport officials reported a sharp drop today in international passenger arrivals — a further blow to the country’s crucial tourism industry, which is one of the top foreign currency earners.

One of the most prominent democracy proponents in the country, Nobel Peace laureate Mohamed ElBaradei, called on the civilian government to resign and for a national unity government to be formed “grouping all the factions so it can begin to solve the problems of Egyptians.”

“Power is now in the hands of the military council, which is not qualified to run the country, and the government, which has no authority,” he said on a TV political talk show late Sunday. For the next six months, “we want see the powers of the military council given completely to a civilian, national unity government, and the military goes back to just defending the borders.”

The Supreme Council of the Armed Forces issued a statement Sunday night, saying it does not intend to “extend the transitional period and will not permit by any means hindering the process of democratic transition.”

The military-backed Cabinet said the elections, due to start on Nov. 28, will go ahead as scheduled.

Activists have been holding occasional protests against the military in Tahrir for months, and some have triggered crackdowns by the military or police.

This weekend’s violence was the most sustained fighting between the two sides. It began when security forces stormed a sit-in at Tahrir staged by several hundred protesters wounded in clashes during the 18-day uprising in January and February and frustrated by the slow pace of bringing those responsible to justice.

“The people had a revolution to live a better life, but look at everything,” said 47-year-old Fayez Mohammed, his eyes red from tear gas. He pointed to rising prices, street violence and lack of accountability against members of Mubarak’s regime.

“Our main demand is a date. When are you leaving power?” he said. “And don’t say, ‘Whenever God wills.”‘

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Associated Press writer Ben Hubbard contributed reporting.