BELGRADE, Yugoslavia -- Yugoslavia's federal government sent troops and armor into the breakaway republics of Slovenia and Croatia yesterday as sporadic incidents of ethnic violence left several people dead and wounded.
Convoys of tanks and armored personnel carriers took control of the borders with Italy and Austria while jets screamed low over the rooftops of Ljubljana, the Slovenian provincial capital, in what officials called an act of "psychological warfare" against the rebel region.
Tanks rolled into Slovenia's main airport early today after defiant citizens set up blockades but apparently did not try to fight the federal advance, the Associated Press reported.
Slovenian officials said the federal government was trying to secure the field so military planes could land. The airport was closed yesterday, a day after Slovenia and neighboring Croatia declared independence.
A duty officer at the airport, Marjan Miklavci, said on Slovene radio that at least 10 tanks had entered the airport outside Ljubljana. He was quoted as saying airplanes had been parked on the runway, presumably by Slovenes seeking to prevent military aircraft from landing.
An Associated Press reporter saw nine Soviet-made T-72 tanks and two armored personnel carriers approach the airport.
The convoy managed to get past the roadblocks set up by Slovenes, one group crossing over fields to the airport. The Slovenian defense forces said tanks rammed through some of the blockades.
Slovene radio said that at one blockade, some of the federal troops went over to the Slovenian side, but did not say how many.
Federal troops in battle gear, using tanks and helicopters, also sealed off at least two areas of Croatia after ethnic violence between Serbs and Croats left at least four people dead and scores injured.
Croatia's independence declaration is opposed by many of the republic's 700,000-strong Serbian minority. A Croatian spokesman said three people were killed and 10 wounded in a dawn gunbattle that raged for several hours after local Serbs stormed a Croatian police station in Glina, 50 miles south of the republic's capital, Zagreb.
A policeman was killed and at least four people were wounded in shooting in the Croatian town of Brsadin near the border with Serbia, the official Tanjug news agency said.
All the old divisions that gave the region its pre-World War I name of the "Balkans Powder Keg" have surfaced afresh and threaten to engulf the 72-year-old country in a civil war conducted by a Lebanon-style array of armies and militias.
The most immediate fear is of clashes between federal troops and the private armies of the self-declared new countries.
Federal troops and armored units stationed in Slovenia were placed on combat readiness. Tanks were stationed on major access roads, overturning barricades erected by local protesters, blocking off several towns and villages and turning back traffic.
Officers were ferried into Slovenia by helicopter to take command of the units. The federal police were given instructions to patrol internal borders between Croatia and Slovenia.
In a statement explaining its actions, the federal government said independence declarations by the two rebel republics "constitute unilateral acts adopted without agreement with the other constituent factors of Yugoslavia and are therefore illegal and illegitimate and all the effects of those acts are null and void."
Slovenia reacted by mobilizing its own territorial army of 70,000, which is equipped with weapons ranging from Kalashnikov assault rifles to helicopter gunships. Between them, Slovenia and Croatia have 140,000 men under arms -- just 40,000 fewer than the national army. The Croatian special forces and armed volunteer units had already been placed on alert.
An immediate flash point is the potential conflict between the federal troops and ethnic militias. "We will not use force first," said Slovenian Interior Minister France Bucar. "But we will defend checkpoints with force if necessary."
Another and more explosive potential flash point, however, was in enclaves in Croatia inhabited by 700,000 Serbs who refuse to recognize Croatia's independence. The Serbs in the area near Zagreb known as Krajina have already declared autonomy.
Representatives from other Serbian enclaves in an area between the Sava and Danube rivers -- the area known as Slavonija, Baranja and Srem -- formed their own "Grand National Assembly" Tuesday night. They declared their own autonomous region and warned of "fatal consequences" should Croatia's armed militia try to impose Croatian law.
The Serbs have formed their own militia and have backing from Serbia, Yugoslavia's largest republic. At least 20 people have already been killed in Serb-Croat clashes in these enclaves over the past two months.
There were signs today that violence was set to escalate. Reports on Croatian radio said several terrorist attacks had taken place, including the machine-gunning of scores of Croatian homes and the blowing up of a railway line.