Police and politicians warned Belfast on Sunday to brace for more bloodshed after a Protestant paramilitary commander and his friend were gunned down because of an apparent feud within his outlawed group.

John "Grugg" Gregg, one of the six regional commanders in the Ulster Defense Association, and Robert Carson, a junior-ranking UDA member, both died Saturday night when the taxi they were riding in was riddled with bullets while stopped at a red light. The taxi driver remained hospitalized Sunday in critical condition.

Police believe the attack was linked to an ongoing feud between the UDA, Northern Ireland's major outlawed Protestant group, and supporters of its ousted west Belfast commander, Johnny "Mad Dog" Adair.

Detectives on Sunday arrested two Adair associates on suspicion of involvement. The hijacked car used by the attackers was found abandoned in Adair's militant Protestant power base, the Lower Shankill district of west Belfast.

A Protestant paramilitary group called the Red Hand Defenders issued a statement Sunday night claiming responsibility for the killings. Police believe the Red Hand Defenders is a cover name used by the UDA, among others.

Feuding involving Adair and Northern Ireland's myriad armed Protestant gangs has claimed more than a dozen lives since 2000. Britain warned that more violence likely will follow.

"The people of Northern Ireland are sick of bracing themselves for yet another spat of brutal killings and shootings amongst criminals," said Northern Ireland Security Minister Jane Kennedy.

Gregg was best known for his 1984 attempt to kill Gerry Adams, leader of the IRA-linked Sinn Fein party. He served 18 years in prison for that attack.

Gregg was among the UDA commanders supporting Adair's expulsion last year after the latter was accused of collaborating with a rival Protestant gang, the Loyalist Volunteer Force, in drug deals and attacks on other UDA members.

Britain ordered Adair back behind bars last month in an effort to quell tensions. But Adair's Lower Shankill UDA unit has continued to clash with other UDA units.

Police linked Adair's supporters to three other attacks on the Belfast-area homes of UDA members this weekend.

The UDA, an umbrella group for anti-Catholic vigilante groups founded in 1971, has an estimated 3,000 members. It called a cease-fire in 1994 after killing several hundred Catholics in an effort to terrorize the IRA's host community.

More than 200 members, including Adair, received early prison paroles because of their professed support for Northern Ireland's 1998 peace accord.

But the UDA remains one of Northern Ireland's major criminal organizations, and Britain said in 2001 that the UDA cease-fire no longer was valid because of attacks on Catholics.

Also Sunday, a bomb exploded close to an army reservist center in south Belfast. Police said they believed Irish Republican Army dissidents opposed to the peace process were responsible. There were no reports of injuries.