The EU and UN yesterday began a two-day push to drum up fresh aid pledges for war-torn Syria and reinvigorate the faltering Geneva peace process as the conflict enters its eighth year.

Donor countries, aid organisations and UN agencies are gathering in Brussels for the seventh annual conference on Syria's future as international inspectors probe a suspected gas attack in the town of Douma, highlighting the brutal nature of the war.

The meeting comes in the wake of strikes by the United States, France and Britain on Syrian military installations, carried out in response to the alleged chemical weapons incident in Douma which has been widely blamed on Damascus.

EU officials hope to beat the $6 billion pledged at last year's gathering, as forces loyal to President Bashar al-Assad launched a new offensive against Islamic State jihadists entrenched in a southern district of Damascus.

The UN has warned that its own appeal for money for humanitarian work in Syria this year is less than a quarter funded, receiving less than $800 million of the $3.5 billion needed.

"Within the resources we can plausibly expect to mobilise this year we cannot meet even all the urgent needs," Mark Lowcock, the head of UN humanitarian agency OCHA said at the start of the conference.