Head, leaders of Syrian Islamist rebel group killed in suicide bombing

The leader of an ultraconservative Islamic rebel group in Syria was killed Tuesday in a suicide bombing along with other of its top officials, its allies said, weakening the ranks of the country's already shaky armed opposition.

No group immediately claimed responsibility for the attack that killed Hassan Aboud and other leading members of Ahrar al-Sham, part of the strongest front that challenged the Islamic State group, which holds wide swaths of territory in Iraq andSyria. But given that forces loyal to President Bashar Assad's government do not typically use suicide bombers, it appeared likely that forces in the murky mix of opposition fighters in Syria's 3-year-old civil war were involved.

The attack struck a high-level meeting of Ahrar al-Sham, or The Islamic Movement of Free Men of the Levant in English, held in the northwestern town of Ram Hamdan in the Syrian province of Idlib, one of its strongholds. A statement from the group said the blast killed Aboud, also known by the nom de guerre Abu Abdullah al-Hamwi, along with 11 other top leaders.

"They were martyred ... in an explosion inside their meeting headquarters," said a statement on the Twitter feed of the Islamic Front, the rebel coalition to which it belonged.

An activist collective called the Edlib News Network, the Britain-based Syrian Observatory for Human Rights and Syrian state media also reported Aboud's death. The activist reports said the men died in a suicide bombing.

The Edlib News Network said over 40 people were killed in the blast. The Observatory, which relies on a network of activists in Syria for its reports, said "tens" of people were killed. Differing casualty figures are routine immediately after attacks inSyria.

Ahrar al-Sham was part of the Islamic Front, an alliance of seven powerful conservative and ultraconservative rebel groups that merged in late November. The Islamic Front wants to bring rule by Shariah law in Syria and rejects the Western-backed Syrian National Coalition, but cooperates with some of their fighters on the ground.

While Ahrar al-Sham was an ultra-conservative group, its leadership, including Aboud, sought to balance "the group's fundamentalist platform with a relatively pragmatic political strategy," said Noah Bonsey, a Syria analyst for the International Crisis Group. Aboud had even once met with a top U.S. State Department official, Bonsey said.

On Wednesday, U.S. President Barack Obama is expected to lay out a plan to the American people on what course of action should be taken to challenge the Islamic State group, which Ahrar al-Sham opposed.

Bonsey said it was unlikely that Ahrar al-Sham would have been a direct recipient of American aid, because, despite its moderation, it still remained too hard-line for the West. But the bombing likely would significantly disrupt or possibly destroy the group as a whole, he said.

"Ahar al-Sham had been one of the best led and most organized, and overall, one of the most effective groups on the ground," Bonsey said. "It's a loss of talent within the rebel spectrum as a whole. Ahrar al-Sham was one of the strongest, if not the strongest rebel group, and the question is, what will it look like going forward?"

Syria's conflict began as large demonstrations against Assad's rule that collapsed into a war with sectarian undertones. Rebels are overwhelmingly from Syria's Sunni Muslim majority. Many in Syria's minority groups have backed Assad or remained neutral, fearing for their fates should rebels come to power.

The conflict has been further complicated by militants of the Islamic State group, whose mass killings, beheadings and targeting of minority groups has sparked international outrage. Obama is now trying to gather an international coalition to challenge the group.

Ahrar al-Sham had blamed the Islamic State group for the killing of one of their leaders in February, a man known as Abu Khaled al-Souri, a confident of former al-Qaida leader Osama Bin Laden.

Meanwhile Tuesday, the new United Nations special envoy to Syria began his first visit to the country, entering Damascus amid heavy exchanges of mortar and shelling between government forces and rebels.

Steffan de Mistura, a Swedish-Italian diplomat, is stepping into a mission that has frustrated two previous high-profile predecessors: Finding a resolution to a conflict that has killed more than 190,000 people and has driven a third of Syria'spopulation — some 9 million people — from their homes.

As the envoy arrived, fighting intensified between government forces and rebels who control suburbs around the capital. Rebels fired mortars into Damascus and the eastern district of Jaramaneh, killing five people, according to the state news agency SANA.

A government warplane shelled the nearby town of Douma, killing at least 13 people, according to a rebel who uses the name Abu Yazan, and the Observatory.

De Mistura replaced Lakhdar Brahimi, who resigned on May 31 after nearly two years of failed efforts to end the war. Brahimi had followed in the footsteps of former U.N. Secretary-General Kofi Annan, who resigned in August 2012.

De Mistura was expected to meet with Foreign Ministry officials and members of Syria's government-approved opposition before leaving Saturday.