COLOMBO, SRI LANKA, JUNE 18 -- The government declared war today on Tamil separatist guerrillas waging a week-old offensive that began with a spate of attacks on police and army bases in the north and east.

"From now it is all-out war," Deputy Defense Minister Ranjan Wijeratne told Parliament in asking for an extension of the existing state of emergency. "We will annihilate the Liberation Tigers of Tamil Eelam, take over the east and then go for the north." But Wijeratne nevertheless held out the possibility of negotiation. "I advise the {Tigers} to stop the fighting and come to the negotiating table before it is too late."

Wijeratne said 600 rebels had been killed since the new fighting broke out June 11. "Our losses have been minimal," he added. Unofficial estimates had put the death toll in seven days of fighting at more than 450, including rebels, members of the security forces and civilians.

Parliament passed the motion for extending the state of emergency, which gives extra powers to the security forces, by a vote of 121 to 1.

Military sources said troops backed by artillery fire and air cover were sweeping through the east, driving away rebels after the collapse of a fragile cease-fire that began Saturday.

The Tigers, with an estimated 3,000 men the largest of several anti-government guerrilla groups, accused the troops of setting fire to houses and the air force of bombing and strafing parts of the northeast. At least seven civilians were killed in the attacks, they said.

After a brief lull in hostilities following the cease-fire, heavy fighting erupted Sunday between the Tigers and troops in several parts of the northeast.

The military accused the rebels of attacking an army camp in eastern Trincomalee district with machine guns, mortars and rocket-propelled grenades and of using an unidentified gas in the assault. At least 450 soldiers, many wounded, were trapped in the camp, the daily English-language Sun newspaper reported.

The Tigers have been fighting for nearly 20 years for a socialist homeland for minority Tamils, many of whom feel discriminated against by majority Sinhalese who control the top government posts.

The government's chief negotiator said that talks underway with the rebels since May of last year came to a standstill last week after the guerrillas failed to observe two cease-fires.