The UK is “confident” that air strikes carried out by Britain, the US and France on suspected chemical weapons facilities in Syria have been successful, the PM has said.
Theresa May also said it had been “right and legal” to take action.
Military bases near the capital Damascus and the city of Homs were targeted, after an alleged chemical attack on the Syrian town of Douma.
Jeremy Corbyn said MPs should have been consulted on the air strike on Monday.
Syrian state media said there had been a “violation of international law”.
Speaking in Downing Street, Mrs May said the “limited and targeted strikes” had degraded Syria’s ability to use chemical weapons.
“This collective action sends a clear message that the international community will not stand by and tolerate the use of chemical weapons,” she said.
Drawing a link with the recent nerve agent attcks in Salisbury Mrs May added: “We cannot allow the use of chemical weapons to become normalised – either within Syria, on the streets of the UK or elsewhere.”
She also said she would make a statement to Parliament on Monday and give MPs a chance to ask questions.
The Ministry of Defence (MoD) said Storm Shadow missiles had been launched by four RAF Tornados at a former missile base, 15 miles west of Homs – where it is thought President Bashar al-Assad’s regime has been stockpiling items used to make chemical weapons.