The United States is reviewing the threat to Americans in Lebanon posed by Hizbullah.

U.S. officials said the State Department has received warnings that U.S. nationals in Lebanon could be abducted or killed in Shi'ite neighborhoods of Beirut. The warning also extended to Shi'ite communities in southern Lebanon.

The warning came amid bloody Shi'ite riots in Beirut in May in which at least five people were killed in clashes with Lebanese authorities.

Hizbullah has blamed the U.S. embassy in Beirut for masterminding the violence, Middle East Newsline reported.

"Due to a series of incidents over the past month, the U.S. Embassy has placed coastal areas south of Beirut off-limits to its staff until further notice," the U.S. embassy in Beirut said. "The embassy recommends that private U.S. citizens avoid the same areas if at all possible."

Officials said U.S. diplomats have also been banned from entering Hizbullah strongholds either in Beirut or in southern Lebanon. The embassy has been monitoring Hizbullah's presence along the Israeli-Lebanese border.

On May 20, the State Department renewed a warning against traveling to Lebanon. Officials said the warning came in wake of Al Qaida-inspired plots to attack the U.S. embassy and American restaurant chains around Beirut.

On Sunday, however, a U.S. delegation of researchers traveled to southern Lebanon to meet Hizbullah commander Nabil Quark. Quark was said to have briefed the delegation on Hizbullah's regime in the south and its war against Israel.