UK urges 'strong' response to alleged Syrian chemical attack

In a call with his French counterpart Jean-Yves Le Drian, Johnson "underlined the urgent need to investigate what had happened in Douma and to ensure a strong and robust international response," the Foreign Office said in a statement.

US President Donald Trump and French President Emmanuel Macron had similarly called for a "strong, joint response" to the suspected chemical attack on Saturday that reportedly left at least 100 dead.

Saturday's attack saw graphic images and videos emerging on social media showing semi-lifeless children struggling to breathe and entire families who had succumbed to the attack on the floors of underground shelters.

Both the Assad regime and its ally Russia have denied the allegations, calling them 'fabrications' and have warned against using them to justify military action. The attack comes one year after sarin gas killed at least 80 in the opposition village of Khan Sheikhoun.

While the Foreign Office statement did not explicitly apportion blame for the attack, it said that Le Drian and Johnson "noted that international investigators mandated by the UN Security Council had found the Assad regime responsible for using poison gas in at least four separate attacks since 2014".

The two "agreed that those responsible for this attack must be held to account" and a UN Security Council meeting on Monday would be "an important next step in determining the international response and that a full range of options should be on the table".

Prime Minister Theresa May's spokesperson described the reports of a chemical weapons attack "deeply disturbing" and said Britain would work with its allies on "a coordinated approach".

Also on Monday, UK charity Save the Children said international powers "cannot continue to allow the slaughter of children by all sides in Syria to continue with impunity".

Sonia Khush, Syria Response Director, said in a statement: "While we can't confirm what happened on Saturday night, it's clear that once again children have been killed and injured in indiscriminate attacks. Our partners report helping children who were choking, foaming at the mouth and convulsing in a chaotic situation.

"We need the nationwide ceasefire that was agreed by the UN Security Council in February implemented immediately, and the UN and ICRC granted access to all areas of Eastern Ghouta, including Douma. Following months of intense fighting, displaced civilians and those who choose to remain in their homes need urgent humanitarian support." 

Eastern Ghouta has been under a ruthless military campaign and siege for the past weeks that devastated the area and killed over 1,600 people, leaving Assad's forces to control more than 90 percent of the former rebel stronghold.

Russia, a stalwart diplomatic backer of the Syrian regime since the start of the war, had put itself forward as a "guarantor" for so-called "de-escalation zones" in Syria, one of which was Eastern Ghouta.