AFP/Beirut

Syrian regime air strikes on Islamic State group stronghold Raqa killed at least 95 people as a government delegation prepared for talks with key ally Russia on Wednesday on relaunching peace negotiations.

The bombing on Tuesday was the deadliest by President Bashar al-Assad's air force in Raqa since Sunni extremist IS fighters seized control of the city last year and declared it their capital.

More than half of the dead were civilians, according to the Syrian Observatory for Human Rights, which monitors the war through a network of sources.

It was unknown how many jihadists were killed.

Raqa was the first provincial capital to fall from regime control, and it was later overrun by IS which has used it as the capital of its self-proclaimed "caliphate" straddling Syria and neighbouring Iraq.

The multi-sided Syrian conflict has killed more than 195,000 people and forced millions from their homes since it began three and a half years ago as an uprising against Assad's regime.

The government has in recent months stepped up its air strikes against IS-held towns in the north and east, with most of the casualties reported to have been civilians.

Raqa has also been the target of repeated air strikes by the US-led coalition fighting the jihadists.

The exiled opposition Syrian National Coalition condemned the strikes as a "brutal massacre", warning that "many seem now convinced that Assad is the major beneficiary of the US-led coalition strikes" against the jihadists.

- Staunch Russian support -

A Syrian regime delegation headed by Foreign Minister Walid Muallem was due to meet Russian President Vladimir Putin at his Black Sea retreat of Sochi on Wednesday.

They were expected to discuss a possible relaunch of peace talks with the opposition, a senior Syrian official said last week.

A second round of UN-brokered talks was held in Switzerland in early 2013 but ended without agreement.

A former leader of the National Coalition, Moaz al-Khatib, is reported to have held talks at the Russian foreign ministry on November 7.

But the coalition has voiced scepticism about prospects for progress.

"We are used to the regime trying to put together its handpicked opposition in Damascus, made of up people close to them," its secretary general Nasr al-Hariri told AFP ahead of the talks.

"This kind of opposition does not concern us. These attempts don't provide any kind of political path to a solution in Syria."

The delegation from Damascus was also expected to push for the delivery of long-sought S-300 anti-aircraft missiles.

Russia has remained a staunch supporter of Assad throughout the uprising that began in March 2011.

Last September, Putin said delivery of the S-300 missiles had been suspended without saying why.

It came after Israeli Prime Minister Benjamin Netanyahu paid a special visit to Russia to ask Moscow to halt the shipments.

The UN and human rights groups have repeatedly called on all sides in the war, including the Assad regime, to stop using weapons that fail to discriminate between civilians and military targets.

- Scenes of carnage -

Amateur video footage distributed by activists in Raqa showed several bloodied bodies laid out on a street near an apparent bombing site, as an ambulance rushed to the scene.

Aid workers in red overalls bearing the Red Crescent symbol could be seen placing the corpses into white body bags.

Strategically located on the river Euphrates, Raqa had a pre-war population of about 220,000 but it is now home to 300,000-350,000 people, including many displaced by the conflict, according to the Observatory.

Since the jihadists first started moving into the city, they have been gradually imposing a brutal yet highly organised system with all the trappings of a state, experts say.

In Iraq, the other main focus of the US-led military campaign against IS, pro-government forces have managed to recapture some of the territory lost in a sweeping June offensive by the jihadists.

However, the militants sill hold large areas of the country, including the key cities of Mosul, Tikrit and Fallujah.