Australia has condemned the Syrian regime for its continued indiscriminate bombing raids on civilians in eastern Ghouta, warning many more people will die if the illegal onslaught continues.

Australia, speaking at its first session as a member of the human rights council, said it was appalled by the deteriorating humanitarian situation in eastern Ghouta, where nearly 400,000 civilians remain under siege and bombardment by the Syrian regime.

“Hundreds of people have been killed by regime attacks in recent days despite the passage of UNSC resolution 2401,” Dr Lachlan Strahan, Charge D’Affaires of Australia’s mission to the UN in Geneva told the council. “International humanitarian law is clear – there can be no justification for such attacks, which have been indiscriminate and disproportionate.”

The human rights council took the extraordinary step of clearing its scheduled agenda to debate the deteriorating humanitarian crisis in Eastern Ghouta.

The rebel-held enclave, near the Syrian capital of Damascus, has been under government siege since 2013. The latest offensive has brought intense bombardment by Syrian and Russian warplanes since 18 February. On 24 February, the UN security council unanimously passed resolution 2401 in favour of a month-long ceasefire, but this has failed to materialise.

Russia, instead has proposed a truce in the fighting between 9am and 2pm each day, and civilian corridors to allow civilians to flee. Even these have not been upheld.

With the ceasefire paralysed, Australia spoke forcefully on the floor of the council, condemning the Syrian regime and telling its key backer, security council member Russia, that it too held responsibility for the carnage so far and for bringing an end to the violence.

“Many more will die if the regime continues its offensive,” Strahan said. “We call for the immediate implementation of the ceasefire agreed by the UNSC to bring an end to the bombardment … and to allow aid to reach Syrians in need.

“The onus is on the regime’s backers, including security council member Russia, to bring an end to this terrible humanitarian crisis.”

The human rights council’s draft resolution, proposed by the UK, highlighted the gross and sustained abuses of human rights by the Syrian regime, including the use of illegal chemical weapons against civilians.

The resolution demanded “free, unimpeded, and sustained access to eastern Ghouta for the United Nations and humanitarian operators to all people in need”.

Twenty-five countries voted in favour of the resolution, four voted against it (China, Cuba, Iraq, and Venezuela), while eight council members abstained.

Russia is proposing a series of amendments, which will be debated and voted upon on Monday.

Human Rights Watch told the council that since 19 February, Syrian and Russian bombardments have killed more than 600 civilians.

Amnesty International told the council that all parties must grant safe passage to civilians wanting to flee, and allow humanitarian access. “The Syrian government has been committing war crimes with total impunity, and will continue to do so as long as it is not held accountable,” Amnesty said.

“The international community must act now to end the carnage. The catastrophic humanitarian situation will continue to deteriorate if parties to the conflict do not abide by international humanitarian law and are not held in check when they fail to do so.”