ZAGREB, YUGOSLAVIA — THE Yugoslav Army said yesterday it would accept an "absolute and mutual cease-fire" with Croatian forces.Tanjug news agency said the truce was agreed in accordance with an EC-sponsored cease-fire pact brokered by former British Foreign Secretary Lord Carrington and signed Tuesday. The announcement that both sides had agreed to the truce came shortly after the key Croatian town of Petrinja near the breakaway republic's capital, Zagreb, fell to Army troops after days of vicious street fighting. Fighting had intensified in Croatia this weekend after the Yugoslav Army pledged to press ahead with "decisive" military action against the rebel republic. Sporadic explosions rocked Zagreb and city defense officials said federal Army troops blockaded in the Marshal Tito barracks fired multiple rocket launchers at the city. The Federal defense minister, Gen. Veljko Kadijevic, made clear in a somber state television address Saturday that the Army would strike hard in Croatia, where 500 people have been killed in three months of fighting. Federal warplanes Saturday attacked the town of Novska, 60 miles southeast of Zagreb, on the main highway to Belgrade, the radio said. The Army has cut the highway, slicing Croatia in half. Fighting and artillery fire was also reported in the Adriatic port of Zadar.