BEIRUT, Lebanon - A Syrian human-rights group says more than 400 people have been killed during a government bombardment of rebel-held areas of the northern city of Aleppo, and more than one-quarter of the victims are children.

Rami Abdurrahman of the British-based Syrian Observatory for Human Rights said Wednesday they counted 401 people killed in 11 days of government bombing of Syria's largest city and its province, including 117 children.

Abdurrahman said the toll was one of the highest, and with the most civilian casualties, of any government assault in Syria's three-year conflict.

The toll is so high because the government was hurling imprecisely aimed, explosive-laden barrels over residential areas, he said.

The Observatory bases its information on a network of activists on the ground.

Other rights groups have given much higher numbers of casualties.

Peace talks

The government has not commented on its use of the so-called barrel bombs, nor on why it began intensely targeting Aleppo. The attack comes weeks before an international conference is expected to bring together Syria's government and opposition groups seeking to overturn the rule of President Bashar al-Assad.

Analysts say the attack may be an attempt to bully civilians to expel rebels from parts of the city they seized in July.

Russian fuel deal

Also Wednesday, Syria's state news agency said the oil ministry had signed a deal with the Russian oil and gas company Soyuzneftegaz to explore in the Mediterranean Sea, in a boost to the war-ravaged country's economy.

SANA's report did not say where the deal was signed, though it said the exploration would take place off the Syrian coast.

Most of Syria's oil and gas fields in the country's east are under opposition control, and the country's oil exports almost have stopped.

Russia is one of Assad's strongest backers.

Israel is already developing recent discoveries of massive offshore deposits in the region, and Lebanon has spoken of trying to develop offshore fields.