"It is about a limited and targeted strike that does not further escalate tensions in the region and that does everything possible to prevent civilian casualties", she said.
The Organisation for the Prohibition of Chemical Weapons has been "working in close collaboration" with United Nations security experts "to assess the situation and ensure the safety of the team", it said.
Four Royal Air Force Tornado jets from the Akrotiri base in Cyprus fired Storm Shadow missiles at a military facility near Homs where it was assessed that Syria had stockpiled chemicals, Britain's Ministry of Defence said.
Syrian state media reported that internal security forces had entered Douma on Saturday and that the town would be secured within hours.
Britain has blamed Russian Federation for the poisoning - a charge vehemently denied by Moscow which has accused London of failing to come up with evidence for its claims.
He also did not rule out further attacks against Syria if the Assad regime continued the alleged use of chemical weapons. "We sent a clear message to Assad and his murderous lieutenants that they should not perpetrate another chemical weapons' attack for which they will be held accountable".
The three countries consulted and collaborated on an assault in which more than a 100 missiles, reportedly targeting specific sites, were launched into Syria after the government was accused of a chemical attack. "This massacre was a significant escalation in a pattern of chemical weapons use by that very awful regime", Trump alleged.
"It was right to take the action that we have done in the timing that we have done", she said.
A YouGov poll for The Times newspaper this week indicated that only a fifth of voters believed that Britain should launch attacks on Syrian military targets and more than two-fifths opposed action.
Meanwhile Labour leader Jeremy Corbyn has said Parliament should have been given a vote ahead of the strikes.
"Bombing can not substitute for diplomacy", he said.
She said that at an emergency cabinet meeting in London on Thursday "we agreed that it was both right and legal to take military action" after hearing legal advice.
In a statement Friday night, U.S. President Donald Trump outlined strikes being carried out against the Syrian regime of Bashar al-Assad after a chemical weapon attack earlier in the week.