Police were searching Sunday for a man who threatened to detonate a bomb at an air base being used by U.S. forces in southern Pakistan.

The man walked into a Muslim religious school near the air base in Jacobabad, 186 miles east of the Afghan border, Sunday morning and told officials he had a bomb strapped to his body and intended to detonate it at the base, police said. He then disappeared.

Some 1,100 U.S. military personnel are stationed at the base as logistical support for coalition forces in Afghanistan.

Military officials called in an additional army unit to guard the base, which reportedly has over half a dozen U.S. fighter aircraft and nearly a dozen helicopters.

The town was the scene of violent anti-U.S. demonstrations after U.S. and allied forces began airstrikes against Afghanistan in October. Local residents have protested several times against the presence of U.S. forces at the military base on the edge of town.