Thousands of Syrian people have staged a mass rally in Damascus to protest at a deadly US raid that killed 8 civilians in a Syrian village.

Syria strongly reacted to the US strike, calling it a "terrorist attack" that resulted in the killing of "innocent civilians."

Demonstrators waved Syrian flags and banners reading "No to American terrorism" and "American democracy: the killing of civilians at Abu Kamal," the border area targeted in Sunday's US raid.

"Colonialists, listen, the people of Syria will never be brought to their knees," chanted the protesters as they gathered in the heart of Damascus.

Security was boosted in the area in Damascus housing the US embassy, which was closed on Thursday due to the demonstration.

On Tuesday, the Syrian Cabinet wrote a scolding letter to the UN Secretary General Ban Ki-moon and the Security Council, slamming United States' Sunday attack that killed the eight civilians including four children.