A car bomb ripped through a police checkpoint west of Baghdad and killed at least four officers today, a day after a group linked to Al Qaeda claimed to have abducted and killed 14 policemen. Two other police officers were killed by a hidden explosive in eastern Baghdad, an indication of the dangers facing police as they increase their presence on the streets to enforce a new security plan. Sunni Muslim insurgents, who accuse the mainly Shiite police and military of atrocities against Sunnis, have made police checkpoints, patrols and training centers frequent targets of attacks.

Prime Minister Nouri Maliki issued an angry response to Friday's mass abduction and slaying of police, which occurred in Diyala province as they were on their way home for leave. The cars in which they were riding were intercepted, and their bodies were found hours later, after a group linked to Al Qaeda claimed to have abducted them. The group said it carried out the attack to avenge the purported rape of a Sunni woman at the hands of Shiite police officers last month.

"This massacre reflects the reality of these gangs acting under the so-called Iraqi Islamic State, who are mere criminals," he said, calling their act the work of "sick minds." Maliki's government has denied the rape accusation, saying the charge was intended to inflame sectarian tensions. Signs of those tensions were evident today in the Shiite neighborhood of Sadr City, where U.

S. and Iraqi military officials are expected to establish a foothold within days as part of the security plan launched Feb. 13.

Sunnis have accused the security forces of unfairly focusing their attention on Sunni areas, with aggressive raids and patrols, while Shiite areas are left alone. Dozens of Sadr City civic leaders gathered to discuss ways they could help the plan succeed. But while they promised to support troops when they set up a base in Sadr City, they also issued a statement calling for the immediate withdrawal of foreign forces from Iraq, or at least a timetable for the withdrawal.

If troops are to remain for long, the statement said U.S. troops and government officials in the country should "come into Islam and declare publicly taking Islam as their religion.

" One Sadr City resident, Sattar Jabbar Sharhan, echoed many residents' concerns that troops would crack down on the Shiite militia that has been protecting the neighborhood. Sharhan also said Iraq's Shiite-led security forces were capable of operating without Americans. "Why Americans?

" he said. "Even if they are with the Iraqi troops, why? I think our troops are capable enough to protect us.

" Also today, U.S. military officials said some "key terrorists" linked to an Al Qaeda cell that had been targeting military helicopters were believe killed in an air strike.

The air raid occurred outside Taji, north of Baghdad, which is the site of a major U.S. air base.

The area around Taji has been the scene of frequent attacks on military helicopters. Since the start of the year, at least seven U.S.

helicopters, including one civilian craft, have been shot down. The military statement said U.S.

aircraft spotted alleged terrorists with vehicles equipped with anti-aircraft weapons and fired at them. It did not say how many of them were believed killed. Times staff writer Raheem Salman, and special correspondents in Hilla and Baghdad contributed to this report.