A series of explosions were heard in Syria's capital Damascus early Saturday even as US President Donald Trump announced strikes on the country were underway.
At least six loud explosions were heard and smoke was seen rising over the Syrian capital, a witness told Reuters.
A second witness said the Barzah district of Damascus, the location of a major Syrian scientific research centre, had been hit in the strikes.
The strikes have hit Syria bases and chemical research centres around Damascus, a war monitor said.
They included an air base west of Damascus near the Lebanese border, a commander in the regional military alliance that backs President Bashar al-Assad said.
The targeted al-Shirai air base is located in al-Dimas, the commander told Reuters.
The attack hit a site in Masyaf, about 170 km (100 miles) north of Damascus, army depots in the eastern Qalamoun region northeast of the capital, the Kisweh area south of Damascus, and a site in the Qasyoun hills overlooking the capital.
The strikes also hit a military research centre and warehouses in Syria's central Homs province.
Three blasts were heard from Homs city after a military research centre and depots were hit, the Syrian Observatory for Human Rights said.
The army's air defences were confronting an attack by the United States, France and Britain,Syrian state TV said.
"Our respected viewers, the Syrian air defences have resisted the US-French-British aggression against Syria that was announced by (USPresident Donald) Trump a short time ago. Our respected viewers, in these moments, the Syrian air defence resist the US-French-British aggression," Syrian state TV announced.
US President Donald Trump on Friday ordered precision strikes targeting Syrian President Bashar al-Assad's chemical weapons capabilities after a weekend poison gas attack that killed at least 60 people on April 7.
Trump said a combined operation with France and Britain was underway.
"A short time ago, I ordered the United States Armed Forces to launch precision strikes on targets associated with the chemical weapons capabilities of Syrian dictator Bashar al-Assad," Trump said in a televised address from the White House.
(With inputs from Reuters)