Surface-to-air missiles are seen over Syria's capital Damascus on April 14, 2018, as the Syrian air defenses were responding to U.S. attacks. (Xinhua/Ammar Safarjalani)

DAMASCUS, April 14 (Xinhua) -- The United States started its military action against Syria's capital Damascus before daybreak Saturday as loud explosions were heard here with "red dots" seen flying from earth to the sky, reported Syrian state TV and Xinhua reporters in Damascus.

As loud explosions were heard across the capital, the Syrian air defense missiles were launched from Mount Qasioun, which overlooks the capital, with smoke rising from areas in Damascus, according to Xinhua reporters on the ground.

The air defense missiles looked like red dots flying from earth to targets in the sky.

The state TV also reported that the Syrian air defense system was responding to the "U.S., French and British aggression on Syria."

The state TV said the Scientific Research Center in Barzeh area northeast of Damascus was hit among other positions, adding that the Syrian air defense system destroyed 13 missiles launched by the United States near the capital.

In the central province of Homs, the TV said no damage was reported as the air defense system responded to the attack that targeted several of the Syrian army's arms depots.

Meanwhile, the TV denied reports that the United States targeted the International Airport of Damascus.

Activists from Syrian Observatory for Human Rights said the U.S. strikes targeted the Scientific Research Centers in Damascus and its countryside as well as in the city of Homs. The UK-based watchdog said military bases and posts of the Republican Guard and the Fourth Division of the Syrian army were hit as well.

The United States has accused Syria of using chlorine gas in an April 7 attack against the rebel-held town of Douma near Damascus, pledging a military strike against the Syrian government forces amid threats of retaliation from both the Syrian forces and Russia.

U.S. defense chief James Mattis said Friday's attack against Syria was a "one-time shot," and the Pentagon has reportedly said that the targets in Syria have been destroyed.

The Syrian state news agency SANA said the attack was a flagrant violation of the international law, adding that Syria has responded to the attack as it responds to terrorists on the ground.

"The triple aggression is doomed to failure and it didn't succeed in saving its terrorist tools in Syria," SANA said, adding that the Syrian people and army will not be terrorized by the U.S. missiles.