 LONDON -- Pro-government forces continued to pound the rebel-held enclave of Eastern Ghouta on Monday, despite a U.N. call for a 30-day ceasefire across Syria.

Airstrikes and artillery shelling have killed at least 31 civilians, including eight children, since the U.N. Security Council adopted the resolution on Saturday demanding a 30-day truce across Syria "without delay," according to Rami Abdurrahman, the director of the Syrian Observatory for Human Rights. Nine members of the same family were killed in Douma on Monday, the watchdog group said.

"After the [U.N.] decision, weapons were used that had not been used in previous days," a spokesperson for the Eastern Ghouta branch of the Syrian Civil Defense, also known as the White Helmets, told ABC News on Monday. "There are children and women that members of the civil defense were not able to pull out from under the rubble because 11 warplanes were not leaving the sky at all. There is blood and pieces of flesh in the streets."

A resident of Douma, who asked that her real name be withheld for security concerns, said she was hiding from the bombardment in her living room, away from the doors and windows.

"Warplanes and helicopters are dropping rockets and artillery shells are being fired, as well," she told ABC News.

In the past week, the Syrian government and its allies have intensified attacks on Eastern Ghouta, killing at least 561 civilians, including 139 children, according to the Syrian Observatory for Human Rights.

On Monday, Russia said it would establish a five-hour daily truce from 9 a.m. to 2 p.m., starting Tuesday. Along with Iran, Russia is Syrian president Bashar al-Assad’s main ally.

On Sunday, the White Helmets said that warplanes dropped missiles containing chlorine on the town of Shayfuniya in Eastern Ghouta.

Doctors said they treated several victims with symptoms consistent with exposure to chlorine -- and that one child choked to death. The Syrian Observatory for Human Rights corroborated the account that several people in the area had signs of choking and one child died.

On Monday, the head of the U.N. called for the ceasefire to be implemented immediately, to ensure the delivery of humanitarian aid and the evacuation of the sick and wounded.

"As I had the opportunity to say in the Security Council itself a few days ago, in particular eastern Ghouta cannot wait," U.N. secretary-general Antonio Guterres told the U.N. Human Rights Council in Geneva. "It is high time to stop this hell on earth."

The recent surge in violence in Eastern Ghouta, which has been besieged by the Syrian government since 2013, is part of president Bashar al-Assad’s campaign to seize Syria’s last remaining opposition-held territories. The Syrian government and Russia say their military offensive against Eastern Ghouta is necessary to overthrow rebels who have been firing mortars on Damascus.