Scores of homes in central Syria's Qusayr are razed to the ground, its shops are smashed, and the smell of gunpowder still hangs heavy in the air.

After Syrian troops and Hizbullah took control of the symbolic insurgent bastion on Wednesday, Qusayr has become a ghost town, a witness told Agence France Presse.

Yemeni authorities released on Thursday 17 of 58 political activists held since the 2011 uprising against former president Ali Abdullah Saleh, an Agence France Presse correspondent witnessed in Sanaa.

As they came out of the central prison's compound, youth activists who have been pressing for their release raised their hands chanting: "Revolt, revolt -- it will go on."

Al-Qaida militants are holding a South African couple abducted last month in Yemen's central city of Taiz, a top security official said on Thursday, adding that investigations are not "very encouraging."

"It's almost confirmed that the two South Africans are now held by al-Qaida men," the official told Agence France Presse.

A hot air balloon accident that killed 19 tourists in Egypt was caused by the "grave" pilot error that caused a gas leakage, a police forensic report has found.

The interior ministry report blamed the manager of the hot air balloon port and the pilot for the February 26 accident that killed the Asian and European tourists.

Three bombings in Baghdad, including a car bomb in a market, killed five people Thursday, the latest in a surge in Iraq violence that has sparked fears of a revival of all-out sectarian war.

Twin roadside bombs in southwest Baghdad killed three people, while a car bomb in a market in the capital's southeast killed two others, security and medical officials said.

Austria will withdraw its troops from the U.N. peacekeeping mission in the Golan Heights, the government said Thursday, after Syrian rebels briefly seized a crossing on the Israel-Syria ceasefire line.

"In light of this, the defense minister said that... the Austrian army's participation in the UNDOF mission can no longer be maintained for military reasons," Chancellor Werner Faymann and Vice-Chancellor Michael Spindelegger said in a statement.

Two U.N. peacekeepers suffered injuries in shelling on Thursday in the Golan Heights ceasefire zone between Israel and Syria, a U.N. peacekeeping spokesman said.

"The two suffered minor injuries from the fallout of heavy weapons fire in the area," U.N. peacekeeping spokesman Kieran Dwyer told Agence France Presse.

France has sent the United States "all the information it has" on what it has billed as proof that chemical weapons have been used in Syria, a foreign ministry spokesman said on Thursday.

The move follows a request on Wednesday from U.S. Secretary of State John Kerry amid mounting pressure for the United States administration to act in response to the evidence of chemical weapons use.

Syrian Foreign Minister Walid Muallem will lead the government delegation at proposed peace talks in Geneva, Russia's top diplomat said Thursday, amid efforts to agree the format and timing of the conference.

"We are continuing to work with the (Syrian) government, which has already announced its readiness to take part in the conference and that the foreign minister will lead its delegation," Lavrov said in comments broadcast on state television.

The International Federation of Red Cross and Red Crescent Societies said on Thursday that all of its appeals to help Syrian refugees are underfunded, and asked for more aid.

"We have several appeals, all underfunded... below 20 percent coverage," Steve McAndrew, head of the IFRC's Emergency Operations for Syria, told a news conference in the Jordanian capital Amman.