Fighters from the al Qaeda offshoot "Islamic State" have launched an attack on a key government airfield in eastern Syria, activists said on Thursday.

The Britain-based Syrian Observatory for Human Rights said at least 19 government troops and seven IS militants had been killed in the attack, which reportedly began overnight with a suicide car bombing on a military position just outside the airfield near the city of Deir el-Zour, the capital of the eponymous province.

It said there had been heavy clashes amid government shelling on the surrounding villages.

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

Source of oil revenue

The miltary air base, which is used by government forces to launch aerial attacks on IS-held cities and towns across eastern Syria, is one of the last remaining areas in the province of Deir al-Zour still under control of President Bashar al-Assad.

State media have so far made no mention of Wednesday's alleged attack, saying only that government forces had on Wednesday inflicted heavy losses on the jihadists in Deir al-Zour city. International journalists are not allowed to enter most conflict zones, making it difficult to independently verify reports coming from the region.

The province, whose oilfields are a major source of revenue for the IS, borders on territories in Iraq that are also controlled by the jihadist group.

The group has continued attacking Syrian government forces and rival rebels, fighting to oust the Assad regime, despite pressure from US-led air strikes.

However, the IS has suffered a number of setbacks in recent weeks, and if the group were to capture the air base in Deir al-Zour, it could provide a boost to morale, as well as consolidate the group's grip on the region.

tj/ksb (AP, Reuters)