Bomb attacks hit near Damascus and air strikes pounded rebel bastions on Wednesday as international divisions were again exposed over how to end an escalating conflict now said to have killed more than 36,000 people.

As UN-Arab League peace envoy Lakhdar Brahimi urged China to do more to help tackle the crisis, talks between French and Russian officials in Paris failed to resolve deep disagreements over President Bashar al-Assad's regime.

Russian Foreign Minister Sergei Lavrov defiantly accused the West of fuelling the violence by insisting on Assad abandoning power.

"If the position of our partners remains the departure of this leader who they do not like, the bloodbath will continue," Lavrov said after talks with his French counterpart Laurent Fabius.

But US Secretary of State Hillary Clinton reiterated the West's position by saying Washington wanted to help the Syrian opposition unite against Assad, while urging it to resist efforts by extremists to "hijack" the revolution.

In a week that has seen unprecedented air strikes, fighter jets again pummelled rebel-controlled areas east of Damascus, where clashes have raged for months.

The raids came a day after 30 civilians, including five children, were killed in air strikes and fighting around the capital's eastern suburbs, said the Syrian Observatory for Human Rights.

Clashes erupted and air strikes hit the northwestern province of Idlib, where rebels attacked highway military checkpoints and battles raged over the rebel-held town of Maaret al-Numan and the Wadi Daif army base.

Fighting also shook the northern city of Aleppo, residents said, and a motorcycle bomb attack near a Shiite Muslim shrine southeast of the capital killed at least eight people and injured dozens, the Observatory said.

A car bomb southwest of Damascus also shook the town of Moadamiyat al-Sham, killing at least one person, it said.

At least 125 people were killed on Wednesday, including 45 civilians, said the Observatory, adding that more than 36,000 people had now died in the 19-month conflict.

An average of 165 people have been killed per day day since August 1, it said, and the overall toll includes nearly 27,000 civilians and armed rebels and more than 9,000 government soldiers.

After the heaviest wave of air strikes yet on Monday, a fighter jet hit targets inside Damascus on Tuesday for the first time, dropping four bombs on an eastern neighbourhood near to an opposition-held suburb.

Analysts say the regime has boosted air strikes in recent days in a bid to reverse opposition gains on the ground, especially in the north, and to prevent the rebels from seizing further territory around the capital.

In Paris, Fabius said the talks with Russia had failed to bridge the divide over what role Assad and his regime should play in Syria's future.

"Yes, there is a difference of assessment on the presence of Bashar al-Assad in a transition government," he said.

Both Russia and China have exercised their veto in the UN Security Council to block resolutions aimed at putting more pressure on Assad.

Visiting Beijing, peace envoy Brahimi urged China to help bring a halt to Syria's violence.

Greeting Foreign Minister Yang Jiechi in front of reporters, Brahimi said he hoped "China can play an active role in solving the events in Syria," without elaborating.

During the talks, Yang said the situation in Syria had reached a "crucial stage" but a political solution was the only way to end the bloodshed.

Brahimi, who succeeded former United Nations chief Kofi Annan after he quit over what he called a lack of international support, is due to present new proposals for resolving the conflict to the Security Council in November.

Members of Syria's fractured opposition, who have struggled to unite the disparate groups opposing Assad, vowed on Wednesday after a conference in Turkey to work for the rapid formation of a government-in-exile to win greater support from the international community.

Speaking during a visit to Croatia, Clinton said Washington was "working very hard with many different elements of opposition inside and outside Syria."

Washington wants to assist the opposition "to unite behind a shared effective strategy that can resist the regime violence and begin to provide for a political transition," she said.

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