Residents of Syria's eastern Ghouta district say they are "waiting for their turn to die."
The besieged, rebel-held enclave near Damascus is enduring one of the most intense bombardments of the Syrian conflict.
The renewed offensive began at the weekend.
Monitor the British-based Syrian Observatory for Human Rights says:
At least 38 people died on Wednesday
At least 310 people have been killed since Sunday night
More than 1,550 have been injured.
The Observatory says the pace of the strikes appeared to slacken overnight, only to intensify again later on Wednesday morning.
Why is eastern Ghouta being targeted?
Because it is the last major area near the Syrian capital that is still under rebel control.
Home to 400,000 people, the densely-populated agricultural neighbourhood on the outskirts of Damascus has been besieged by government forces for years.
There has been a massive escalation in bombardment since Sunday, including rocket fire, shelling, air strikes and helicopter-dropped barrel bombs.
It is one of a group of "de-escalation zones" under a diplomatic ceasefire initiative agreed by Assad's allies Russia and Iran with Turkey. However, a rebel group formerly affiliated with al Qaeda is not included in the truce and has a small presence there.
Conditions in eastern Ghouta, besieged since 2013, had increasingly alarmed aid agencies even before the latest assault.
Shortages of food, medicine and other basic necessities are causing suffering and illness.
Has the Syrian government said anything?
Yes. Damascus and its ally Russia, which has backed President Bashar al-Assad with air power since 2015, say they do not target civilians.
They also deny using the inaccurate explosive barrel bombs dropped from helicopters whose use has been condemned by the UN.
Rebels have also been firing mortars on the districts of Damascus near eastern Ghouta, wounding seven people on Wednesday, state media reported. Rebel mortars killed at least six people on Tuesday.
A commander in the coalition fighting on behalf of Assad's government told the Reuters agency overnight that the bombing aims to prevent the rebels from targeting the eastern neighbourhoods of Damascus with mortars.
It may be followed by a ground campaign.
"The offensive has not started yet. This is preliminary bombing," the commander said.
Has the United Nations said anything?
Yes. The organisation has denounced the bombardment, which has struck hospitals and other civilian infrastructure.
Officials warn the attacks could amount to war crimes.
Secretary General Antonio Guterres has appealed for an "immediate suspension of all war activities in eastern Ghouta." Speaking to the UN Security Council, he described residents as living in "hell on earth".
Guterres expressed support for a Swedish and Kuwaiti push for the 15-member council council to demand a 30-day ceasefire in Syria. Diplomats said the council could vote on a draft resolution in the coming days.
However, Assad's veto-wielding ally Russia has called the proposal "not realistic".
The International Committtee of the Red Cross is calling for humanitarian access to Ghouta, especially to reach wounded people in critical need of treatment.
"The fighting appears likely to cause much more suffering in the days and weeks ahead. This is madness and it has to stop," said Marianne Gasser, the ICRC's head of delegation in Syria.
Medical charity Médecins Sans Frontières says 13 hospitals have been hit and damaged or destroyed in the past three days.
What they are saying
"We are waiting our turn to die. This is the only thing I can say," - 22-year-old Abu Salah, whose wife is five months pregnant with their first child.
"The estimated arrival time for the plane to reach the most-bombed parts of eastern Ghouta - Harasta - two minutes from now," a typical alert sent at 4.41 pm by the Syrian Civil Defence air strike warning system.