DAMASCUS (Reuters) - The United States said on Wednesday it will close its embassy in Damascus to the public on Thursday due to security concerns amid rising tensions between the two countries following a U.S. raid on Syria.

A demonstration is planned in the Syrian capital on Thursday to protest against the raid which Damascus said killed eight civilians.

Syria had earlier ordered an American school and cultural center to be shut down in an apparent response to the U.S. action on Sunday.

Relations between Washington and Damascus are already strained by U.S. accusations that Syria is failing to stop militants, including al Qaeda fighters, from entering Iraq.

The U.S. embassy in Damascus said in a statement it will be closed on Thursday due to “increased security risk.”

An embassy spokesman earlier said that Americans in Syria must be aware that “unforeseen events or circumstances may occur that could cause the U.S. Embassy in Damascus to close to the public for an unspecified period of time.”

“The U.S. Embassy in Damascus remains concerned about the continued threat of terrorist attacks, demonstrations and other violent actions against U.S. citizens,” he said.

The spokesman declined to comment on whether the number or status of U.S. diplomats in Syria could change.

The demonstration planned for Thursday is to be staged by groups describing themselves as independent. A U.S. official has said that a smuggler of foreign fighters into Iraq was believed to have been killed in the attack.

Diplomats said the crisis could escalate into tit-for-tat retaliation if the protest turns violent. But a source familiar with the planning for the event said it will be held away from the embassy.

“There are no plans to march on the embassy. An American flag may be set alight but the protest will be peaceful,” the source said.

WAITING GAME

Responding to Sunday’s raid, Syria decided to close an American school with 450 students and an American cultural center in Damascus. Hundreds of U.S. nationals live in Syria. Thousands more have dual U.S.-Syrian nationality.

Syrian villagers pray over coffins during a mass funeral for victims of a raid in the village of Sukaria in the Bou Kamal area, near the Iraqi border October 27, 2008. REUTERS/Khaled al-Hariri

The official news agency SANA said Damascus informed Washington on Wednesday of its decision to close the two facilities.

Syria also has called on the U.N. Security Council to take action to prevent a repeat of the attack in which military helicopters flew over the border and struck a farm just inside Syrian territory.

The Syrian Foreign Ministry called in foreign ambassadors for a meeting on Wednesday to explain the measures Damascus has taken against the United States, SANA said.

Deputy Foreign Minister Fayssal al-Mekdad said Syria was waiting for an official explanation from Washington and Baghdad about “the unacceptable violation of Syrian sovereignty” before taking any more measures.

Washington recalled its ambassador to Syria following the assassination of former Lebanese Prime Minister Rafik al-Hariri in February 2005. The United States also has Syria on a list of states that support terrorism and Damascus has been under U.S. sanctions since 2004 over its support for militant groups.

Thousands of protesters attacked the U.S. embassy in Damascus in 1998 during a demonstration against U.S.-led military strikes on Iraq.