Hundreds of protesters staged a sit-in Saturday in the Masnaa-Bar Elias area in Lebanon’s eastern Bekaa valley, the main road linking Beirut to Damascus, blocking the passage of fuel tankers to war-torn Syria.

The demonstration, organized by the Association of Muslim Scholars, was staged in the eastern Bekaa Valley to stem fuel supplies intended for forces loyal to Syrian President Bashar Assad.

The Syrian army's use of surface-to-surface missiles on Aleppo is part of a bid to advance on the northern city, swathes of which have fallen into rebel hands since mid-2012, a watchdog said Saturday.

"The army has been trying for weeks to come closer to Aleppo via its eastern entrance, in order to assault it. Elite troops are being sent... but so far the army has been unsuccessful," said Syrian Observatory for Human Rights director Rami Abdel Rahman.

The umbrella opposition National Coalition on Saturday condemned world powers for failing to act to stop the slaughter in Syria, as missiles killed at least 29 in second city Aleppo.

The remarks by spokesman Walid al-Bunni came after the Coalition had said it would form a government to run "liberated areas" of Syria and was pulling out of several international meetings in protest against world "silence".

International peace envoy Lakhdar Brahimi said Friday that a devastating bomb blast in the Syrian capital was a "war crime" that had left about 100 people dead.

The toll given by Brahimi was grimly higher than the 61 dead given by Syrian activists after a suicide bomber staged the attack Thursday near the entrance to President Bashar Assad's ruling party offices.

The United Nations High Commissioner for Refugees said on Friday that at least 305,753 refugees have fled the warn-torn neighboring country and came to Lebanon since the start of the conflict in Syria.

The UNHCR's weekly report on the situation of refugees in Lebanon elaborated that the majority of Syrians and Palestinians reside in the north of Lebanon with their number reaching 112,384.

French freelance photographer Olivier Voisin, who was seriously wounded in Syria last month, was in critical condition Friday after an operation in Turkey, media watchdog Reporters Without Borders (RSF) said.

"Voisin was injured by shrapnel from an exploding shell while covering the operations of a katiba (armed opposition group) near Idlib," in northern Syria at the end of January, RSF said in a statement.

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.

At least 12 people, including children, were killed on Friday and dozens wounded when three surface-to-surface missiles struck in the northern Syrian city of Aleppo district, a watchdog said.

"At least 12 bodies have been recovered so far and there are more than 50 people wounded," Syrian Observatory for Human Rights director Rami Abdel Rahman told Agence France Presse by phone.

Phalange Party MP Sami Gemayel lashed out on Friday at Lebanese authorities for not suspending diplomatic ties with the neighboring country Syria after the judiciary demanded the death penalty for a Syrian security official.

Gemayel wondered how the Syrian Ambassador to Lebanon, Ali Abdul Karim Ali, wasn't expelled or summoned.

Human Rights Watch on Friday demanded unfettered access to Syrian prisons after a prominent peace activist died in custody and another was feared dead.

Omar Aziz, a 64-year-old husband and father of three, died of heart complications after he was transported to Harasta military hospital in the Damascus suburb of Mazzeh on Saturday, a relative told the watchdog.