KGB Office Besieged by Armenians : Soviet Union: A man is killed in the riot following a protest over a chemical plant leak. The incident breaks a 3-month lull in violence in the republic.

Armenians armed with gasoline, burning torches and flare guns besieged KGB headquarters in their capital and tried unsuccessfully to destroy it as violence erupted anew in the Soviet Caucasus republic after a nearly three-month lull, official media and residents reported Sunday.

The Soviet state security agency said one man was mortally wounded when a homemade bomb he was carrying blew up in his hands, also seriously injuring a girl. But some Armenian activists blamed KGB agents for the blast during the Saturday night violence.

KGB Chairman Vladimir A. Kryuchkov called the attack on his agency’s building in Yerevan “an onslaught by bandits.” It came as the leadership of President Mikhail S. Gorbachev was preoccupied with forcing another Soviet republic, Lithuania, to renounce its decision to secede, and the Kremlin was clearly bracing for more trouble.

“The KGB of the U.S.S.R. has taken rapid measures for the furnishing of help to the collective of co-workers of the KGB of Armenia,” Kryuchkov, a member of the ruling Politburo, told Armenian KGB employees in a message also carried by the official Tass news agency.

The Caucasus has been on the boil for two years because of the bitter dispute over who should govern Nagorno-Karabakh, a predominantly Armenian region that has been part of neighboring Soviet Azerbaijan since 1923. Hundreds were killed in January in anti-Armenian attacks in Azerbaijan’s capital of Baku, armed warfare between the two ethnic groups and a Soviet army attack to restore order.

A KGB account carried by Tass said the Yerevan rioters were angered by the KGB’s arrest of four Armenians on charges of stealing weapons from a military unit, but Armenians interviewed by telephone said the genesis of the weekend unrest was outrage over a local environmental hazard.

On Saturday morning, a valve exploded at the Nairit chemical plant in Yerevan’s suburbs, releasing toxic chloroprene gas into the air, Alexander Arzumanyan of the Armenian National Movement said. More than 100 people fell ill and were hospitalized, and many Yerevan residents felt sick, Arzumanyan said.

At news of the leak, the Armenian National Movement and two other non-governmental organizations, the Ecological Union and the Greens’ Union, organized a Saturday evening rally in Yerevan’s Freedom Square. Up to 150,000 people came and demanded an emergency session of the republic’s legislature to fire Prime Minister Vladimir Markayants, who did not obey the Parliament’s order that the Nairit plant be shut by the end of 1989.

As the rally broke up, a group of about 1,000 people set off for KGB headquarters, about 15 minutes away on foot in central Yerevan. “They brought gasoline to the building,” Arzumanyan said.

Spurred on by “provocative calls to liquidate the KGB,” the crowd, mostly youths, threw rocks and flaming torches at the multistoried building and made numerous attempts to storm it, Tass said. Incendiary bullets were also hurled and signal flares fired inside, touching off fires, it said.

The two-hour attack left dozens of smashed windows, holes in the building’s stone facade, and wrecked and charred furniture inside, according to footage of the damage shown on state-run television’s evening news program, “Vremya.” The windows and doors were protected by iron grillwork, which apparently stymied attempts to enter.

The girl injured in the bomb explosion was in a state of shock, the KGB said. Arzumanyan charged that state security agents had tossed “explosive packets” customarily used in military training down at their assailants, but that accusation could not be independently verified.

The KGB said that, although its units were in a state of military preparedness, they did not use their weapons.

The attackers eventually withdrew after armored personnel carriers and tanks appeared near the building, Yerevan residents said. The capital was reported calm but tense Sunday night, with no sign of armored vehicles on the streets.

The KGB said criminal proceedings had begun to bring the rioters to account, and Moscow Radio said the Armenian branch of the state security forces vowed that such “outbursts” would be dealt with firmly. It blamed “the criminal world, disguising itself as a public patriotic movement,” for the rioting.

Armenian Communist Party chief Suren Arutyunyan was fired earlier this month as tensions increased before parliamentary elections scheduled for May 20. Protesters last week surged into the Parliament building to mark the first anniversary of the killing of 20 pro-independence demonstrators in neighboring Georgia.