SANAA, Yemen >> Rebel Shiite Houthis battled soldiers near Yemen’s presidential palace and elsewhere across the capital Monday, seizing control of the country’s state-run media in a move an official called “a step toward a coup.”

The fighting near the palace marks the biggest challenge yet to the government of President Abed Rabbo Mansour Hadi by the Houthis, who seized the capital, Sanaa, during their advance in September across parts of Yemen. Many believe deposed President Ali Abdullah Saleh, ousted in a deal after Arab Spring protests, backs their campaign.

The battles saw the convoys of Yemen’s prime minister and a top presidential adviser affiliated with the Houthis come under fire, as well as Houthi fighters take over Yemen state television and its official SABA news agency, Information Minister Nadia Sakkaf said.

“This is a step toward a coup and it is targeting the state’s legitimacy,” Sakkaf told The Associated Press.

The violence began early Monday, with witnesses saying heavy machine gun fire could be heard as artillery shells fell around the presidential palace. Civilians in the area fled as columns of black smoke rose over the palace. The fighting caused a number of casualties as ambulance sirens wailed throughout Sanaa.

A medical official in Sanaa said the fighting killed at least three people. The official spoke on condition of anonymity because he wasn’t authorized to speak to journalists.

Well-known Yemeni activist Hisham Al-Omeisy, who lives near the presidential palace, said the fighting began after 6 a.m. (0300 GMT, 10 p.m. EST) with a shell hitting a hill controlled by the Houthis. They responded with heavy artillery fire, he said.

He later saw two bodies in civilian clothes just outside his house. He said he couldn’t tell if the dead were civilians or Houthis, because the rebels also dress in civilian clothing.

Later, “I thought it was all quiet and I left my house. But a shell landed right near me,” he told The Associated Press on Monday afternoon.

The Houthis’ al-Maseera satellite television channel aired a report accusing the army of opening fire without reason on a militia patrol in the area of the presidential palace, sparking the violence. A Yemeni military official, speaking to the AP on condition of anonymity as he wasn’t authorized to brief journalists, said the Houthis provoked the attack by approaching military positions in the area and setting up their own checkpoints.

Hadi doesn’t live at the palace, but his home nearby quickly was surrounded by additional soldiers and tanks amid sporadic gunfire, witnesses said. Schools located near the clashes also closed as Houthi rebels manned checkpoints throughout the city. Many families remained trapped in their homes.

“People are leaving on foot, searching for safety,” resident Tarfa al-Moamani said.

Sakkaf later told the AP that Hadi reached a cease-fire with Houthi rebels, though that apparently disintegrated into further gunfire. Prime Minister Khaled Bahah’s convoy also came under fire after leaving Hadi’s home for a meeting with a Houthi representative, but he was unharmed, Sakkaf said.

Foreign ambassadors also appeared to be attempting to negotiate an end to the fighting.

“Working to promote cease-fire and political negotiations,” a message on British Ambassador Jane Marriott’s Twitter account read. “Challenging times. And all most Yemenis want is food and a job.”

The spark of the latest spasm of violence appears to be rooted in the Houthis’ rejection of a draft constitution that divides the country into six federal regions. On Saturday, the Houthis kidnapped one of Hadi’s top aides to disrupt a meeting scheduled for the same day that was to work on the new constitution.

Monday’s battle comes a day after Hadi chaired a meeting in which he demanded the army defend Sanaa, SABA reported. It wasn’t clear whether Hadi, who has made similar calls in the past, was issuing a new order for security services to take back control of Sanaa from the Houthis.

Hadi and Houthis accuse each other of not implementing a U.N.- brokered peace deal calling for Hadi to form a new national unity government and reform the country’s government agencies as Houthis withdraw their fighters from cities they seized. Houthis also demand integration of their militias into Yemen’s armed forces and security apparatus, something Hadi strongly opposes.

Houthis also accuse Hadi of financing and harboring al-Qaida militants. Hadi’s government says the Houthis use the accusation as an excuse to seize more territory.

“The two sides have hit a dead end,” said al-Omeisy, the activist. “Everyone is strong-headed and everyone has their finger on the trigger. It was only a matter of time.”

Hadi was elected as a president in 2012 after a popular revolt toppled Saleh, who is a Zaydi, a branch of Shiite Islam that exists almost solely in Yemen. Houthis, who are Zayidis, represent about 30 percent of Yemen’s population.

Saleh waged six-year-war against Houthis that ended in a cease-fire in 2010. Now, however, the old foes appear to have joined forces to challenge Yemen’s traditional power players, including top generals, tribal alliances and the Islamist Islah party, the Muslim Brotherhood’s branch in the country.

The U.N. Security Council last year put Saleh on a sanctions list, along with two Shiite leaders, for destabilizing the country. Saleh’s representatives have denied the allegations.

Security officials, speaking on condition of anonymity to discuss intelligence matters, said they believed tribal fighters loyal to Saleh were racing into Sanaa to back the Houthis in the fighting.

Yemen, the Arab world’s poorest country, is also home to al-Qaida in the Arabian Peninsula, considered by the U.S. to be the most dangerous arm of the terror group. That group has said it directed the recent attack against the French satirical magazine Charlie Hebdo in Paris “as revenge for the honor” of Islam’s Prophet Muhammad.

The U.S. has carried out a campaign of drone strikes in the country targeting suspected militants. Civilian casualties from those strikes have angered Yemenis.

Associated Press writers Maamoun Youssef, Maggie Michael and Sarah El Deeb in Cairo contributed to this report.