Rebel Serbs in Croatia launched a heavy artillery attack Monday on Karlovac, and Serb-Croat fighting flared elsewhere in the republic, U.N. officials reported.
Eighteen mortar rounds and eight rockets fell on Karlovac, 30 miles southwest of Zagreb, said Simo Vaatainen, a spokesman for U.N. peacekeepers.Croatian TV reported several casualties but gave no details.
Earlier in the day, the Serbs threatened "massive retaliation" if the Croatian army does not withdraw from Citluk and Divo-selo, the Croatian Serb army said in a statement carried by the Yugoslav Tanjug news agency.
Croat troops last week captured the two villages, near Gospic on the edge of Serb-held Croatia, triggering the worst Serb-Croat clashes in eight months.
The two sides fought a six-month war in 1991, ended by a shaky truce patrolled by some 14,000 U.N. peacekeepers.
Rebel Serbs still hold about one-third of Croatia, which they occupied with the help of the Yugoslav federal army in the 1991 war.
Croatian officials are impatient over the United Nations' failure to enforce a peace plan under which they expected to regain control of Serb-held Croatia.
Vaatainen said there was also fighting early Monday around Medak, 15 miles south of Gospic.
And the Croatian government-run news agency HINA reported that Serb forces fired 20 artillery rounds on Sunja, a town 45 miles southeast of Zagreb. There was no immediate confirmation from the United Nations.
Over the weekend, Serb rockets struck Zagreb suburbs, signaling the Serbs' ability to strike at the Croatian capital. No deaths occurred in the suburbs, but at least eight people died in Karlovac.
On Sunday, the Croatian Serb army based in Knin, Croatia, listed more than 50 "military targets" it said could come under fire, including seven targets in the capital.
In neighboring Bosnia, meanwhile, Croats and Muslims clashed around Mostar, which the Croats envision as the capital of their Bosnian mini-state.