Nairobi, Kenya ? U.S. Embassies on Tuesday warned of possible terror attacks against two hotels in Kenya and a housing compound for Westerners in Saudi Arabia. Kenyan police said they were investigating reports that terrorists had packed a truck with explosives for an imminent attack.

U.S. Embassy spokesman Peter Claussen said U.S. authorities received an anonymous tip on Monday detailing the threats in Nairobi.

In Riyadh, Saudi Arabia, terrorists had the Seder Village compound under “active surveillance,” the U.S. Embassy spokeswoman in Saudi Arabia, Carol Kalin, said.

Kalin said the embassy had barred its American employees and dependents from visiting housing compounds in the capital between the hours of 6 p.m. and 6 a.m.