BEIRUT - Airstrikes in the Syrian capital, Damascus, left at least seven people dead Monday as activists reported a third straight day of escalations by pro-government forces against opposition-held areas inside and around the capital.

Jets believed to belong to the Russian or Syrian Air Forces pounded the Barzeh and Qaboun neighbourhoods in the northeast corner of the capital, levelling several buildings, and also wounded at least 12 people, the activist-run Barzeh Media Center and Britain-based Syrian Observatory for Human Rights reported.

The side-by-side Barzeh, Qaboun, and Tishreen neighbourhoods form one of the last two footholds of the Syrian opposition inside the Damascus city limits.

The two neighbourhoods connect to a vast, opposition-held district in the suburbs of the capital through a network of smuggling tunnels, according to Syria researcher Aron Lund, in a report for the U.S.-based Century Foundation policy institute.

Pro-government forces have so far failed to collapse rebel defences inside the Eastern Ghouta district, despite besieging them there since 2013.

The Syrian Civil Defence first responders, also known as the White Helmets, released a video showing its volunteers trying to rescue a girl from under the rubble of a collapsed building after an airstrike on the Tishreen neighbourhood.

Also on Monday, the Russian military reported the deaths of four of its servicemen when they their vehicle was struck by a roadside in the centre of the country last Thursday.

The loss raised the total Russian combat casualties so far in Syria's war to 27.

The four died when they were travelling as part of a Syrian military convoy to the central city of Homs on Thursday from the Tiyas air base, which is close to the ancient town of Palmyra held by the Islamic State group.

The Russian Defence Ministry said the bomb was detonated by remote control. Two other servicemen were wounded in the blast.

Palmyra, about 60 kilometres (37 miles) away, is one of the focal points of the battle against the extremist group. No group has claimed responsibility for the attack, but blame is likely to fall on IS.

Moscow launched its military operations in support of President Bashar Assad's forces in September 2015. The Russian military has touted its air power as the backbone of its intervention, but its technicians, military advisers, and police forces have helped to clear and secure territory as well.

Russian media estimate that more than 4,000 servicemen have been deployed in Syria based on voter rolls from Russia's September 2016 parliamentary elections.

The Islamic State group overran Palmyra, prized for its ancient Roman archaeological ruins, for a second time last December. The front between the government and Palmyra is now about 16 kilometres (10 miles) west of the town, according to the Britain-based Syrian Observatory for Human Rights monitoring group.

The Observatory said the al-Qaboun neighbourhood was targeted as well.

News from © The Associated Press, 2017