Fresh air strikes hit Syria's Aleppo city early Monday, an AFP correspondent said, after US Secretary of State John Kerry arrived in Geneva in a bid to halt the mounting carnage.

More than a week of fighting in and around Syria's second city has killed hundreds of civilians.

Heavy air strikes hit rebel-held east Aleppo in the early hours of Monday, AFP's correspondent there said, but there were no immediate reports of casualties.

Several neighbourhoods, including the heavily populated Bustan al-Qasr district, were struck. It was not clear if Syrian or Russian jets carried out Monday's raids on the rebel-held area.

Rebel shelling of government-controlled western areas of Aleppo city late Sunday killed three civilians including a child, the Syrian Observatory for Human Rights said.

Growing violence in and around Aleppo has killed more than 250 civilians and threatened both a UN-backed peace process and a fragile ceasefire.

Kerry landed in Geneva late Sunday for talks with Arab foreign ministers and UN peace envoy Staffan de Mistura in an urgent push to end the bloodshed.

"We are talking directly to the Russians, even now," Kerry said after a week in which Moscow refused US calls to rein in its ally, Syrian strongman Bashar al-Assad.

Aleppo was initially left out of a deal to "reinforce" a February 27 truce between the government and non-jihadist rebels.

The freeze in fighting, announced on Friday, applied to battlefronts in the coastal province of Latakia and Eastern Ghouta, near Damascus.

State television reported a Syrian army announcement on Monday that the freeze has been extended for another 48 hours in Eastern Ghouta, until 1:00 am Wednesday (2200 GMT Tuesday).

The same "freeze" is set to hold until 1:00 am Tuesday in Latakia, a regime stronghold.

The head of Moscow's coordination centre in Syria said on Sunday that talks to include Aleppo had begun.

"Currently active negotiations are underway to establish a 'regime of silence' in Aleppo province," Lieutenant General Sergei Kuralenko told Russian news agencies.

More than 270,000 people have been killed since Syria's conflict erupted in March 2011 with protests demanding Assad's ouster.