More than 1,200 civilian casualties in Syria's Eastern Ghouta since Feb. 4: UN

A total of 92 of these civilian deaths allegedly occurred in just one 13-hour period on Monday.

The figures are far from comprehensive and represent only those cases the UN Human Rights Office has managed to document through the "chaos and destruction" in Eastern Ghouta, it said.

UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein said hundreds of thousands of civilians who have been trapped for over five years under siege and deprived of their most basic needs, are now facing relentless bombing in Eastern Ghouta.

Dozens of air strikes and hundreds of ground strikes reportedly hit residential areas in many parts of besieged Eastern Ghouta on Monday and Tuesday, and have continued into Wednesday, said the UN office.

This has led to the displacement of many civilians in areas where there is no safe haven, it said.

According to reports, civilians are seeking shelter underground where they are largely deprived of food and sanitation, the UN human rights body said.

Zeid said international humanitarian law was developed precisely to stop this type of situation, "where civilians are slaughtered in droves in order to fulfil political or military objectives."