The Islamic State group has tightened the noose on a regime-held enclave in eastern Syria, overrunning part of the city of Deir Ezzor and advancing on its vital airbase, a monitor said Wednesday.
"IS seized the Al-Sinaa neighborhood of Deir Ezzor on Tuesday evening and fighting is continuing on the edge of the airport," the Syrian Observatory for Human Rights said.
An estimated 200,000 civilians are believed to remain in government-held districts of Deir Ezzor, where they have been living under siege by IS since March 2014.
The jihadists, who also control nearly all the surrounding province, have made repeated attacks on the government enclave and in January seized the suburb of Al-Bgheliyeh.
But their efforts to capture the city's airbase have so far been repulsed by elite regime troops.
There has been growing concern for the besieged civilian population and, in January, Russia announced that it had equipped Syrian military transport aircraft to carry out aid drops to the city.
On April 10, the World Food Program said it had carried out its first ever successful high-altitude airdrop, to deliver 20 tonnes of food aid to government-held neighborhoods.