A Syrian rebel commander has accused the West of being complicit in the "unprecedented massacres" committed by President Bashar Assad's forces by refusing to arm the rebels with anti-aircraft weapons.

Rebel officer Ahmed al-Fajj, a brigadier-general in the regular Syrian army before his defection "in the first days of the revolution," spoke in the rebel Free Syrian Army-held village of Atmeh on the Turkish border.

Yemeni President Abdrabuh Mansour Hadi said late on Tuesday that he is ready for dialogue with militants of al-Qaida, but only if they give up their weapons and show repentance.

"I've always said that despite the blood that has been shed, the homes that have been destroyed and the people that have been displaced, we would consider dialogue on condition that they give up their weapons, announce their repentance... and stop protecting armed groups," Hadi said in a televised address.

Pro-government militiamen executed at least 16 civilians in their homes in Damascus before dawn on Wednesday, the Syrian Observatory for Human Rights said.

"Militiamen burst into their homes in the Barzeh neighborhood at 5 a.m. (02:00 GMT) and shot them dead," Observatory chief Rami Abdel Rahman told Agence France Presse.

Bombings and shootings mainly targeting Iraqi security forces killed eight people on Wednesday, among them a senior police officer, security and medical officials said.

The violence comes a day after a wave of attacks against members of the security forces left nine police and soldiers dead and 11 wounded.

U.S. Secretary of State Hillary Clinton's pointman for Syria, Fred Hof, is stepping down at a crucial time as world powers seek to end the conflict in the Arab nation.

"I can confirm that he is going to be retiring," a senior State Department official said late Tuesday.

Two suicide bombs struck the heavily guarded Syrian army headquarters in the heart of Damascus on Wednesday, killing four guards and sparking a gunbattle between troops and rebels, state media said.

A rebel officer and a rights group said the audacious attack which also left 14 people wounded was an inside job, while an Islamist rebel group said five of its fighters including a suicide bomber died in carrying out the assault.

French President Francois Hollande on Tuesday called for U.N. protection for "liberated zones" under opposition control in Syria.

Hollande made the call in a speech to the U.N. General Assembly in which he said the Syrian conflict, Iran's nuclear drive and the terrorist threat in Mali and the Sahel region were major emergencies facing the world.

The emir of Qatar on Tuesday called for an Arab intervention force to be sent to Syria to halt the escalating conflict.

Sheikh Hamad bin Khalifa al-Thani, a key backer of the Syrian opposition, made the call at the U.N. General Assembly after U.N. leader Ban Ki-moon said the conflict had become "calamity" that threatens global peace.

Germany urged the world community meeting at the U.N. General Assembly in New York on Tuesday to stand together to find a way to end the war in Syria and stop Iran from getting a nuclear bomb.

Foreign Minister Guido Westerwelle said Iran should face tougher economic sanctions targeting its financial, trade, transport and energy sectors to force it to engage in serious negotiations on its alleged weapons program.

Iraq's cabinet on Tuesday decided to provide humanitarian aid to war-torn Syria and launch a relief campaign via the Iraqi Red Crescent, government spokesman Ali al-Dabbagh said in a statement.

The cabinet decided "to provide humanitarian aid and begin a popular campaign of humanitarian relief for the brotherly people of Syria, via the Iraqi Red Crescent," Dabbagh said, without providing further details.