Death of Syrian rebel leader delays ISIL evacuation in blow to UN efforts

A U.N.-sponsored deal to evacuate more than 2,000 fighters, most of them with the Islamic State in Iraq and the Levant (ISIL), from rebel-held parts of south Damascus has been delayed after a rebel commander was killed, a monitor said Saturday.

The planned pullout, which was supposed to start on Saturday, was the first of its kind between Syrian authorities and ISIL. It would have marked a significant success for the government of President Bashar al-Assad, increasing its chances of reasserting control over a strategic area 2.5 miles south of the center of the capital.

The delay deals a blow to U.N. efforts to end a years-long government siege of parts of the city controlled by a patchwork of rebel groups, which has impeded the flow of food and humanitarian aid, starving many people to death.

The evacuation plan fell through after Zahran Alloush, head of the rebel Army of Islam group, was killed in an airstrike that targeted the group's headquarters during a meeting. He was instantly killed along with a number of commanders from the Ahrar al-Sham and the Faylaq al-Rahman groups.

The Britain-based Syrian Observatory for Human Rights monitoring group said it was unclear in the immediate aftermath whether the airstrike was launched by Syrian or Russian warplanes. The Syrian military claimed responsibility. However, some sources told Al Jazeera that Russian fighter jets were responsible.

"The martyrdom of Sheikh Zahran Alloush should be a turning point in the history of the revolution and rebel groups should realize they are facing a war of extermination by (Russian President Vladimir) Putin's regime," said Labib Nahhas, a senior member of the Ahrar al-Sham group.

"The next stage will witness the liquidation of those leaders who began the uprising," wrote Abu Hassan al-Muhajer, another senior member of the group on Twitter.

Alloush's death is a blow to insurgents fighting to topple President Bashar al-Assad and a boost to government forces who have been bolstered by the Russian military intervention in Syria in the past few months. Syrian government forces have been on the offensive in several parts of the country since Russia began its military campaign in late September to shore up Assad's forces.

The Army of Islam took part earlier this month in a meeting held in Saudi Arabia to agree on an opposition delegation that would negotiate with Assad's government representatives in peace talks in January in Geneva. The Syrian government describes the group as "terrorists" and has said it will not negotiate with such factions.

The United Nations and foreign governments have stepped up efforts to broker local ceasefires and safe-passage agreements toward a wider goal of ending the civil war, in which more than 250,000 people have been killed.

The civil war was sparked by a Syrian government crackdown on a pro-democracy movement in early 2011. ISIL fighters have used the chaos to seize territory in Syria and Iraq. About 4.3 million Syrians have fled their country.

The U.N. Security Council on Dec. 18 unanimously approved a resolution endorsing an international road map for a Syrian peace process, a rare show of consensus among major powers.

U.N. Syria mediator Staffan de Mistura, announced in a statement Saturday that the peace talks would start on Jan. 25 in Geneva. The statement said he aims to convene representatives of the Syrian government and "the broadest possible spectrum of the Syrian opposition and others".

"He counts on full cooperation of all the relevant Syrian parties in this process. Continuing developments on the ground should not be allowed to derail it," the statement said.

In a separate development that underlined the rapidly changing military situation, a U.S-backed alliance of Syrian Kurds and Arab rebel groups said it had captured a dam from ISIL on Saturday, cutting a main supply route of the militants across the Euphrates.

Since the alliance was formed last October, its fighters have launched several major offensives against ISIL with the ultimate goal of capturing Raqqa.

Spokesman Colonel Talal Selo said the seizure of the dam, with the backing of U.S.-coalition planes, helped isolate the militants' strongholds in northern Aleppo from their territories east of the Euphrates river, where Raqqa is located.

ISIL has come under intensifying military pressure in recent weeks, but a new message purporting to come from its leader said airstrikes by Russia and a U.S.-led coalition had failed to weaken it.

"Be confident that God will grant victory to those who worship him, and hear the good news that our state is doing well. The more intense the war against it, the purer it becomes and the tougher it gets," said the audio recording, described as being by Abu Bakr al-Baghdadi.

It slammed Saudi Arabia's efforts to set up a coalition of Muslim nations to fight his group. "If it was an Islamic coalition, it would have declared itself free from its Jewish and Crusader lords and made the killing the Jews and the liberation of Palestine its goal," the message said.

The authenticity of the message, posted on Saturday on Twitter accounts that have published ISIL statements in the past, could not be verified. The last such online public message said to be by Baghdadi was posted in May, and he has been reported injured or killed several times in fighting.

Al Jazeera with wire services