Nearly 400,000 civilians are trapped as Syria's government and its allies pound the besieged Eastern Ghouta district, a suburb of Damascus, with air raids and artillery.
Ground forces have been deployed in an effort to remove the rebels who have controlled the enclave for five years.
Here is what is happening - and why:
What is happening?
- Siege: Eastern Ghouta has been under siege by the Syrian government since 2013, and is the last rebel stronghold near the capital.
- Chronic food and medicine shortages have devastated Eastern Ghouta with severe cases of malnutrition.
- De-escalation zone: Turkey, Russia and Iran agreed in 2017 to designate Eastern Ghouta a "de-escalation zone", in which Syrian and Russian fighter jets were expected not to fly.
- Relentless bombing: On Sunday, February 19, Syrian forces backed by Russian warplanes escalated the offensive on Eastern Ghouta with a relentless bombing that killed hundreds of people within days.
- The bombing, which Amnesty International said amounted to war crimes, has damaged or destroyed six hospitals and medical centres across the city, residents say.
- UN resolution: On Saturday, February 25, the UN Security Council - including Russia - voted in favour of a resolution calling for a 30-day ceasefire "without delay".
- Ground offensive: Also on Sunday, Syrian forces launched a ground offensive targetting areas on the edges of Eastern Ghouta to make it easier for their ground forces to advance.
- As of Monday, February 26, Syrian forces have "not been able to take an inch of territory" in Ghouta, Al Jazeera's Zeina Khodr reported.
- Government forces have allegedly used mortar shells, barrel bombs, cluster bombs, and bunker-busting munitions.
- Chlorine gas: Syria's Civil Defence rescuers, also known as the White Helmets, said victims in Eastern Ghouta were showing symptoms "consistent with exposure to toxic chlorine gas".
- Russian Foreign Minister Sergey Lavrov described allegations of gas use "bogus stories".
How many casualties?
- As of February 26, the death toll in the past three months has exceeded 700 civilians in Eastern Ghouta, Anadolu's news agency reports.
- This includes 185 children and 109 women.
- Syrian government officials say "terrorists" are using civilians as human shields.
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Story Al Jazeera News
Related project: Damascus Church Aid