BEIRUT – Syrian government forces gained more ground in an assault on eastern Ghouta near Damascus on Saturday as they seek to defeat the last major rebel enclave near the capital, a war monitor and a news service run by Lebanon’s Hezbollah said.

The Syrian war, which has killed hundreds of thousands of people since 2011, has escalated on several fronts this year as the collapse of Islamic State has given way to other conflicts between Syrian and international parties.

The U.N. Security Council demanded a 30-day countrywide ceasefire a week ago, but has failed to take effect.

Damascus, backed by Russia and Iran, has been waging one of the deadliest offensives of the war in eastern Ghouta, killing hundreds of people in a fierce air and artillery bombardment over the last two weeks.

Ground forces including the army’s elite Tiger Force have been attacking from the eastern edge of the besieged enclave, where the United Nations says 400,000 people live.

The Jaish al-Islam rebel group said in a statement its fighters had withdrawn from positions in two areas, one of them in al-Shayfouniya, due to intense bombardment. It accused Syrian leader Bashar al-Assad and Russia of waging a“scorched earth” campaign.

The military news service run by Hezbollah, a Lebanese group that fights on Assad’s side, named three other areas it said the Syrian army had captured at the eastern and southeastern rim of the rebel enclave.

With no sign of decisive Western pressure to halt the assault, eastern Ghouta appears on course to eventually fall to the much more heavily armed government side, which has recaptured many other areas using the same military tactics.

Russia has called for daily, five-hour“humanitarian” ceasefires in eastern Ghouta, and says rebels have prevented civilians from leaving. Rebels deny this. The U.S. State Department has called the Russian plan a“joke”.

Damascus says it is fighting terrorists who have escalated their shelling of government-held areas of the capital.