A humanitarian aid convoy has not been able to unload supplies to residents trapped inside Syria's Eastern Ghouta, as government warplanes resumed bombarding the enclave, killing at least 70 people, according to a monitor.

Described as the "bloodiest" day since a Russian-sponsored truce failed to stop the onslaught and since a UN Security Council resolution was unsuccessful at implementing a 30-day ceasefire, Syrian government forces resumed the shelling of the Damascus suburb for the 16th consecutive day on Tuesday.

The Syrian Observatory for Human Rights (SOHR) said the bombardment of the enclave has killed more than 70 civilians since Monday evening.

Residents of Eastern Ghouta, which lies to the east of Damascus, have previously voiced their scepticism of a Russian-proposed "five-hour daily humanitarian pause" that began last Tuesday.

The pauses were meant to create "humanitarian corridors" to allow the evacuation of those seeking medical treatment and the entry of aid convoys, but air raids have continued to target civilians and residential areas.

The resumption of the aerial campaign on Monday came shortly after 46 trucks sent by the International Committee of the Red Cross (ICRC), the Syrian Arab Red Crescent and the United Nations managed to pass through a government-controlled checkpoint for the first time in nearly a month.

But aid workers said the Syrian army confiscated many of the supplies on board.

According to Mahmoud Adam, a spokesperson for the Syrian Civil Defence, also known as the White Helmets, the convoy filled with desperately needed medical supplies and food was forced to rush out as Syrian government forces resumed the shelling of the Damascus suburb.

As a result, nine trucks were prevented from unloading surgical supplies and medicines, as well as 5,500 bags of food and flour, enough to feed about 27,500 people.

Officials from international aid organisations confirmed that the government had blocked the offloading of about 70 percent of medical supplies, preventing trauma kits, surgical kits, insulin and other vital material from reaching the area.

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The area, home to 400,000 people, had been under siege by the government ever since armed opposition groups took control of it in mid-2013.

The White Helmets and SOHR said at least 30 people appeared to be suffocating from a suspected chlorine attack that struck the area on Monday night.

According to Adam, the attack targeted residential areas.

SOHR, a UK-based war monitor, said the death toll could rise as civilians were still being retrieved from under the rubble.

Meanwhile, claims that Syrian troops and pro-government allies had taken control of more than one-third of the enclave has been described as "inaccurate" by activists on the ground.

"Battles between the rebels and the pro-government troops are still being fought in a hit and run manner," one journalist in Douma told Al Jazeera, adding that control of some of the territories was quickly changing.