Ulster police put on alert as two rebels are killed

Police went on alert in Northern Ireland Monday after a guerrilla group threatened to avenge the killing of two of its unarmed leaders who were shot to death by police after a car chase.

After the Irish National Liberation Army issued the threat, a prominent Roman Catholic politician in the British-ruled province called on police chiefs to deny they had set up a special unit to kill suspected guerrillas. The Marxist INLA claimed its two men were gunned down in cold blood and said it would avenge their deaths ''with unmerciful ferocity in the coming weeks.''