Syrian and Russian forces kept up military pressure on rebel-held Eastern Ghouta as their controversial unilateral truce failed to yield a humanitarian breakthrough.

More than 40 trucks loaded with aid were unable to reach the 400,000 people living in the battered enclave, prompting fresh calls for a United Nations ceasefire to be implemented.

A five-hour daily “pause” announced by Moscow on Monday has led to a reduction in the bombardment that killed hundreds in only a few days and sparked global outrage last month.

But a corridor offered by Russia for civilians to flee remained ostensibly empty for a third day running, with distrust running high on both sides.

Jan Egeland, the head of the UN’s humanitarian taskforce for Syria, said he hoped aid convoys may be able to go to Eastern Ghouta “in the next few days”.

“We may have the first facilitation letter, permit from the government, to go to (the main Eastern Ghouta town of) Douma in a very long time,” he said, while stressing “five hours is not enough” of a window.

Syrian aircraft carried out strikes Thursday before the 9:00 am start of the daily “truce”, killing nine civilians, according to the Syrian Observatory for Human Rights, a Britain-based war monitor.

Ground battles were also taking place in Al-Shaifuniyah which lies in the enclave’s northeastern region and has been extensively destroyed in recent days.

A spokesman for the Syrian Civil Defence volunteer rescuers, known as the “White Helmets”, said access to the area had been very difficult.

“There is hardly any life there. It is completely destroyed and there are people under the rubble,” Siraj Mahmud told AFP.

The Russian daily “pause” falls far short of a 30-day ceasefire voted for by the United Nations Security Council on Saturday and yet to be implemented.

The United States on Thursday called on Moscow to pressure Syrian President Bashar al-Assad’s regime to respect evacuation attempts.

“The failed ceasefire called into question Russia’s commitment to de-escalate violence and negotiate a political solution,” Pentagon spokeswoman Dana White said.

“We do not seek a conflict with the Syrian regime, but we call on Russia to restrain the Assad regime, de-conflict counterterrorism operations with the coalition, and de-escalate the remaining battlefields of the Syrian civil war.”

Washington is asking the UN Security Council to set up a new inquiry of chemical weapons attacks in Syria following reports of suspected chlorine use in Eastern Ghouta, according to a draft resolution obtained by AFP yesterday.

The Syrian government has denied using chemical weapons and Russia has questioned UN findings that it carried out sarin and chlorine attacks.