BAMAKO, Mali >> Isolated for centuries by the harsh desert that surrounds it, Timbuktu now finds itself even more cut off from the rest of the world.

Rebels who captured the city in northern Mali in April have imposed a form of hard-edged Islamic rule, prompting many residents to flee in fear and changing the face of what had been a tolerant and easygoing destination that drew tourists from around the world.

Women are now forced to wear full, face-covering veils. Music is banned from the radio. Cigarettes are snatched from the mouths of pedestrians. And the look of the ancient mud-brick town is changing. An ancient monument, the shrine of a 15th-century saint, has been defaced, bars have been demolished and black flags have been hung around town to honor Ansar Dine, or Defenders of the Faith, the radical Islamist movement that emerged from the desert and turned life upside down.

“There is no liberty,” said Abdoulaye Ahmed, a tailor who fled Timbuktu and came to Mali’s capital last week. He added that the Islamist rebels “are constantly circulating with their guns. This is scaring people. The town is sinister.”

The situation is said to be especially troubling for women in Timbuktu. “Women are living in terrible fear,” said Baba Aicha Kalil, a well-known civic activist who is still living in the town, which once had a population of more than 50,000 but has experienced a significant exodus since the rebels moved in.

“They want to put a veil on everything,” Kalil said, reached over a crackly telephone line from Timbuktu, which is about 440 miles northeast of Bamako, at the edge of the Sahara. “They are everywhere, everywhere with their guns.”

All of northern Mali, an area the size of France, has been in the hands of a loose coalition of Islamists and nomadic Tuareg rebels since late March, when resistance by the Malian Army collapsed after a coup d’etat by junior military officers in the capital.

Since the takeover, however, the Islamists of Ansar Dine, supported by al-Qaida, have gained the upper hand over the Tuaregs, and they are aggressively promoting their brand of Islamic law, or Shariah.

Black billboards with Quranic inscriptions have replaced advertisements, residents said. Leading figures in the regional al-Qaida affiliate, al-Qaida in the Islamic Maghreb, have also been spotted there.

A Swiss missionary who was among the last Westerners in Timbuktu was kidnapped in April by gunmen said to have been acting under the orders of the al-Qaida faction. She was later released, after negotiations.

The area is not considered safe for Westerners, and Western journalists have not been there since the Islamist takeover. The al-Qaida offshoot has taken in tens of millions of dollars in ransom payments from Western governments over the last decade, and it was still holding over a dozen hostages in the desert, those with knowledge of the region said.

Kalil said that when the Islamists encountered young people of the opposite sex together, they have forced them to marry on the spot.

“We don’t want the Shariah here,” she said. “Truly we are living in misery. Personally, I am deeply concerned.”

Alpha Sane Haidara, a farmer with deep ties to the region, said: “They have brought the population to heel through terror. I’ve seen them beat up youth watching television in the street.”

Restrictions range from the petty to the serious. In the northern town of Gao, Ansar Dine followers defaced the ear of a woman for wearing a short skirt and flogged men who drank alcohol and were accused of petty theft, Human Rights Watch reported.

Mahaman Alidji Toure, a history teacher at a leading school in Timbuktu, said in a telephone interview, “They’ve told us our trousers can’t descend to our ankles.” He added, “If they find you with a cigarette, they will take you directly to the Islamic police.”

A spokesman for Ansar Dine in Timbuktu angrily rejected the picture drawn by residents and said that if people were fleeing the town, it was because they feared the U.S. might bomb the Islamists who now controlled it.

“We have bad memories of you because of Fallujah and Afghanistan,” the spokesman, Sanda Ould Boumana, said by telephone. “You are not well placed to talk about liberty, when we see what is happening in Guantanamo, Iraq and Palestine.”

Boumana added that “when you accept that there is Islam, you have to accept that there is Shariah.” He said that “if Shariah obliges us to cover women, we are obliged to apply it,” adding, “We have not chosen you as judge.”

Al-Qaida “are our Islamic brothers,” Boumana said.

Ever since the coup, Mali, a nation of 14 million that until recently was considered a democratic model in Africa, has been in administrative chaos, with a power vacuum in the south and a would-be breakaway state in the north. Two weeks ago, the junta’s leader, Capt. Amadou Sanogo, promised to step down, lured by a lucrative deal brokered by Ecowas, a regional alliance of West African states.

But the disarray here in the capital was underscored two weeks ago when the interim president, Dioncounda Traore, was severely beaten by pro-junta activists. He was sent to Paris for treatment, and had not returned.

In a recent report, Human Rights Watch documented a large number of rapes and other abuses immediately after the Tuareg takeover, by armed men speaking the Tuareg language and driving cars with the flag of the Tuareg rebel movement, which is known as the MNLA. Among the disturbing accounts, a 14-year-old girl in Gao described being abducted from her home and repeatedly gang-raped by MNLA rebels.

Although the MNLA is still present in the principal northern towns, Timbuktu, Gao and Kidal — and has thoroughly looted the former offices of the Mali government in Timbuktu, down to the air-conditioners, according to residents — it is Ansar Dine, led by a former Tuareg military commander named Iyad Ag Ghaly, that is aggressively promoting its brand of Shariah and exercising most authority.

Boumana, the Ansar Dine spokesman, said that the Islamists were now “negotiating” with the MNLA over power sharing, and that Ansar Dine did not reject the rebel group’s notion of an independent state in northern Mali, which it calls Azawad, “as long as there is total application of Shariah.”

But he quickly dismissed the idea that Ansar Dine might retreat or give up control of Timbuktu. “It is not our preoccupation that other states accept us,” Boumana said. And in any event, there is no military threat to the northern rebels’ supremacy.

The Malian army, weak and fragmented after the coup, is in no position to take on the rebels and Ansar Dine, diplomats in the capital said. The United Nations said that more than 160,000 Malians have fled to the neighboring countries of Mauritania, Burkina Faso and Niger, with many living in refugee camps, and that more than 140,000 were displaced in Mali itself.

In the meantime, residents say that Timbuktu has taken on the air of a ghost town.

Most stores have closed, and streets are deserted. With banks also shuttered, money is running out. The traditional evening gatherings of young men who drink tea and chat on doorsteps have dispersed.

Haidara, the farmer, encountered at a cafe in Bamako, was nonetheless preparing to head back to Timbuktu. “It’s my city,” he said, “and it’s my land.”