In battleground second city Aleppo, air raids and artillery fire hit rebel-held districts until approximately 2:00 am (2300 GMT Monday), an AFP correspondent said.

Residents spent the night huddled together in their apartments, sharing news about the collapsing truce by messenger.

On Tuesday morning, loud booms were heard intermittently across the city.

In the government-held west of the city, an AFP correspondent reported the sound of shelling in the Mogambo district.

Aleppo -- like other major front lines in Syria -- had been relatively calm for the first few days after the truce brokered by Moscow and Washington came into effect on September 12.

Violence slowly escalated late last week, culminating at the weekend in deadly air strikes on Aleppo and a US-led raid that killed scores of Syrian soldiers fighting the Islamic State group in the east.

Fighting also intensified in the rebel-held eastern suburbs of Damascus, where the army announced a major military operation on Monday just hours before declaring the ceasefire over.

An AFP correspondent in the area heard clashes through the night into Tuesday morning.

Artillery fire also hit the rebel-held central town of Talbisseh, activist Hassaan Abu Nuh said.

In the northwestern province of Idlib, activist Nayef Mustafa said that planes had circled over the town of Salqin, which is held by Syria's former Al-Qaeda affiliate in alliance with Islamist rebels.

"It's calm now, but there was machinegun fire by military aircraft overnight," Mustafa told AFP.

"The ceasefire has collapsed and people are getting ready to be hit by barrel bombs. This is our situation."

The US-Russia truce deal had been billed as the best chance to put an end to more than five years of conflict, in which more than 300,000 people have been killed.

The army declared an end to its ceasefire on Monday evening.

Hours later, a convoy delivering aid to besieged civilians in Aleppo province was hit by an air strike, which killed 12 Red Crescent volunteers and drivers, and destroyed at least 18 trucks.

Bitter Syrian opposition says world ignoring plight
New York (AFP) Sept 19, 2016 - Leaders of Syria's embattled opposition reacted with bitter scorn Monday, accusing the world of ignoring their people's plight as a week-long truce in their country's civil war collapsed.

Addressing a political meeting on the sidelines of the UN General Assembly, the head of the opposition umbrella group known as the High Negotiations Committee (HNC) said the ceasefire had never been respected anyway.

"Enough is enough," Riad Hijab told international diplomats. "The world is content to look on without reacting, when it should assume its responsibilities and put an end to the actions of this criminal regime."

The 23-nation International Syria Support Group (ISSG) is to meet in New York on Tuesday to push for a negotiated end to the five-year-old war that has left more than 300,000 Syrians dead and driven millions from their homes.

But already on Monday, Syrian leader Bashar al-Assad's military had announced an end to a week-old ceasefire that was negotiated between Washington, which backs the rebels, and Moscow, which favors the regime.

"How many UN Security Council resolutions have been passed? They were in vain," Hijab declared.

"Russia and Iran are spilling Syrian blood, the regime bombards hospitals and drops thousands of barrel bombs and other banned weapons. The world just looks on."