Syrian activists say government helicopter gunships have dropped bombs on the Syrian city of Aleppo, killing at least 10 people and wounding many others.

An Aleppo-based activist who goes by the name Abu Raed told the Associated Press news agency that a barrel bomb struck a shop that sells gasoline and diesel, causing a fire that burned bystanders on Thursday.

Abu Raed said the strike on the Qadi Askar neighbourhood killed at least 10, while the Britain-based monitoring group Syrian Observatory for Human Rights said as many as 18 people died.

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The aerial attack comes as government forces and rebels clashed near Aleppo's intelligence headquarters, which the opposition had tried to seize in an attack, a security source said.

A Syrian military source confirmed the "ongoing clashes" in the area after "a fierce attack was launched by the army this morning against (rebel) gunmen positions, killing and wounding many of them."

There were no immediate reports confirming the number of casualties.

The attack on the intelligence offices -- a frequent target of the rebels -- began with a huge explosion in a tunnel that caused part of the building to collapse. An assault by rebels followed but was repelled by security forces.

On Wednesday rebels also launched an attack on the air force intelligence headquarters in western Aleppo, leaving at least 20 members of government forces and 14 rebels dead.

Flurry of diplomacy

As the clashes continue, a UN delegation visited Aleppo to push efforts for a ceasefire in the northern city, which was once Syria's commercial hub but has been divided between regime and rebel forces since fighting erupted in mid-2012.

Opposition forces have earlier rejected the ceasefire plan proposed by UN envoy Staffan de Mistura, saying they instead want a "comprehensive solution" that includes the ouster of President Bashar al Assad.

Meanwhile in Moscow, Russia's foreign ministry said that it would host talks between representatives of the Assad government and rebels in April. 

"Representatives from a larger section of the Syrian opposition," are expected to take part in the talks, said Alexander Lukashevich, spokesman for the foreign ministry.

Deputy Foreign Minister Gennady Gatilov told news agency RIA Novosti that members of the exiled opposition Syrian National Coalition, which did not take part in the first round of talks in January, were "considering coming to Moscow" for the meeting.

The fractious opposition has been trying to consolidate their power, with the president of the National Coalition for Syrian Revolutionary and Opposition Forces, Khaled Khoja announcing on Thursday that his group is trying to ally with Syria-based opposition groups to boost their legitimacy.

Khoja told Reuters news agency that the group's goal was still for Assad to leave power, but that it was no longer a precondition to begin talks.

Despite having only tenuous links with fighters on the ground and seen as out of touch with the general population, the National Coalition remains one of the main parties in international discussions to end the almost four-year-old civil war that has killed more than 200,000 and displaced millions.

Source: Agencies