A suicide car bomber hit a police checkpoint Friday in western Ramadi, killing at least 20 people - two of them policemen - and wounding as many as 30, police in the Anbar provincial capital said. Anbar province has been a stronghold of the Sunni insurgency but many tribes in the region recently switched allegiance, with large numbers of military-age men joining the police force and Iraqi army in a bid to expel al-Qaida in Iraq fighters. Suicide bombings are an al-Qaida trademark. Police opened fire as the suicide car bomber sped toward a checkpoint, five kilometers west of Ramadi, according to police Col. Tariq al-Dulaimi. Nearby buildings were heavily damaged and police were searching the rubble for more victims of the 11:15 a.m. attack. The attack was launched a day after the Islamic Army in Iraq, a key insurgent group, issued an Internet statement highly critical of the Islamic State of Iraq, the radical umbrella organization of insurgent and terrorist factions in the country. The statement signaled a deepening rift among radical Sunni groups and was issued as a response to Abu Omar al-Baghdadi, the leader of the Islamic State of Iraq, who accused the Islamic Army last month of "undermining the activities of the Islamic State and harming the jihad movement in the country," according to the Site Institute, which monitors radical Islamic Web sites. Al-Qaida in Iraq has recently carried out nine chlorine-laden bomb attacks against what it considers turncoat Sunni police in Anbar province. It was also believed responsible for an attack that killed a commander in the 1920 Revolution Brigades.