DAMASCUS  - Syria's opposition National Coalition said Friday it will form a government to run "liberated areas" of the country, as least 12 people were killed and dozens wounded in a missile strike on the northern city of Aleppo.

International peace envoy Lakhdar Brahimi, meanwhile, said a devastating bomb blast in Damascus on Thursday was a "war crime" which had left about 100 people dead.

"We agreed to form a government to run the affairs of liberated areas," spokesman Walid al-Bunni said after a meeting in Cairo, adding that the Coalition will meet on March 2 to decide on the composition of the government and to choose its head.

Coalition members said the meeting would be held in Istanbul, while Bunni said it was hoped the government would be based in rebel-held territory of northern Syria.

The Coalition had been discussing a proposal by chairman Ahmed Moaz al-Khatib to hold direct talks with President Bashar al-Assad's regime. But while saying that while peace negotiations could accommodate "honourable members of the Baath Party and the political apparatus", the group insisted "Assad and the security and military command cannot not part of any political solution."

Khatib had offered to talk to regime officials without "blood on their hands" - an initiative welcomed by the Arab League and the United States, as well as Iran and Russia, both close to the Damascus regime. On the violence in Aleppo, Syrian Observatory for Human Rights director Rami Abdel Rahman said, "at least 12 bodies have been recovered so far and there are more than 50 people wounded."

The Britain-based Observatory said the number of victims was likely to rise, as many people were trapped under the rubble of collapsed buildings in the eastern district of Tariq al-Bab.

Elsewhere, eight civilians were killed in air strikes on Harasta just northeast of Damascus, and warplanes pounded the eastern Damascus district of Qaboon in a bid to push back rebel forces.

In the southern province of Daraa, 10 people were killed by shelling that targeted the Grand Mosque in the town of Harak, the Observatory said. The watchdog, which collects reports from a wide network of activists and medics on the ground, gave an initial toll of 78 people killed nationwide on Friday.

Despite the ever-rising brutality of the conflict, which has left an estimated 70,000 people killed, demonstrations continue to be held every Friday nationwide.

Thousands of Syrian protesters took to the streets on Friday with chants, banners and cartoons of President Bashar al-Assad to vent their anger at Lebanon's Hezbollah and the international community. In the Turkish border town of Ain al-Arab, demonstrators, including young girls and dancing teenagers, shouted for freedom as they held aloft Kurdish flags alongside the Syrian revolution banner in a video posted on YouTube.

In the Idlib town of Kfar Nabal, which has seen deadly air raids in the past week, demonstrators carried banners in Arabic and English. "World! Your carelessness produced extremists like Assad. Now, we need extremists to get rid of your products," read an English banner held by men and boys standing in front of a bombed-out building.

The latest violence came a day after one of the bloodiest days of the conflict, in which 287 people were killed nationwide, including 61 people whom the Observatory reported dead in a suicide bombing in the central Damascus district of Mazraa.

UN-Arab League peace envoy Brahimi said he "strongly condemns the savage and horrible explosion in Damascus yesterday, which resulted in the killing of around 100 and the injuring of two hundred and fifty civilians. "Nothing could justify such horrible actions that amount to war crimes under international law," he added in a statement. Both the regime and its opponents have blamed the attack near the entrance of the ruling Baath party's main offices on "terrorists."

Another 22 people were killed in an apparently coordinated triple bombing targeting security headquarters in the northern Damascus district of Barzeh the same day, including 19 members of the forces, said the Observatory.

Meanwhile, Human Rights Watch (HRW) demanded unfettered access to Syrian prisons after a prominent peace activist died in custody and another was feared dead.

Omar Aziz, 64, died of heart complications after he was transported to a military hospital. Before his November arrest, he had been delivering humanitarian aid to the beleaguered Damascus suburbs.

"A constellation of abuse surrounds each incident of arbitrary detention in Syria, from the government's unwillingness to even acknowledge who is in their custody, to widespread torture and chilling reports of deaths in detention," HRW said.