Nigeria's police chief has ordered increased security at all foreign missions in the country, following violent protests at U.S. embassies in the Middle East.

Police chief Mohammed Abubakar said Thursday he is directing commanders to ensure “water-tight security in and around all embassies and foreign missions in Nigeria as well as other vulnerable targets.”

Islamist radical group Boko Haram has carried out many deadly attacks across northern and central Nigeria in the past three years, including one on U.N. headquarters in Abuja in August of last year.

The U.S. embassy in Abuja issued a warning Wednesday, saying extremists may target U.S. citizens and other Westerners in Nigeria.

Last week, Boko Haram threatened to attack employees of Voice of America in Nigeria.

The group also claimed responsibility for attacks that damaged more than 30 mobile phone towers. Boko Haram accused the companies of helping security agents track down and arrest its members.