Updated

Saudi security forces have defused a bomb placed in a telephone booth in the capital Riyadh (search), a security official said Monday.

A bomb squad defused the bomb on Sunday night, the official said, speaking on condition of anonymity.

The bomb was found by a Saudi man in the telephone booth next to a gas station in Sultana Street in eastern Riyadh.

Saudi authorities have been on a heightened state of alert following four homicide bombings last year that killed 52 people, including the assailants.

The attacks on May 12 and Nov. 8 targeted housing compounds for foreigners. Saudi and U.S. officials blamed Saudi exile Usama bin Laden's Al Qaeda (search) terror network.

Saudi Arabia came under intense pressure after the Sept. 11, 2001 (search), terror attacks on the United States, which were carried out by 19 plane hijackers, 15 of whom were Saudis.

Saudi authorities have detained hundreds of people in a crackdown on alleged militants and urged wanted persons to surrender. Since the May 12 attack, the Interior Ministry has bolstered security around embassies, government buildings and foreigners' housing complexes.