U.N. Suspends Flights to Bosnian Capital : Balkans: Attack on planes in Sarajevo raises fears that Christmas Day cease-fire may not hold.

In the most troubling sign to date that the latest cease-fire in Bosnia-Herzegovina may be in jeopardy, the U.N. Protection Force suspended flights into Sarajevo on Saturday after gunfire struck two of its aircraft.

One of the Ilyushin-76 jets was hit in the tire of its landing gear--presumably after takeoff, because it was discovered only upon return to Zagreb--and the other took at least one bullet in an engine, U.N. spokesman Michael Williams said at mission headquarters here. There were no injuries.

The shootings, the first targeting of U.N. aircraft since former President Jimmy Carter’s peace mission three weeks ago, prompted U.N. commanders to suspend all flights for an indefinite period.

“There is some speculation it was Serbs being drunk because of the holiday,” one U.N. official said here, referring to Saturday’s observance of Orthodox Christmas. “The military are not reading too much significance into it at this point.”

But some observers said they doubt that inebriated gunmen could have hit both white planes operating in snowy Sarajevo, Bosnia’s capital, with random celebratory gunfire and speculated that the attacks were a deliberate provocation.

U.N.-mediated negotiations have so far failed to shore up the cease-fire that took effect Christmas Day and has mostly been holding, except in the embattled Bihac region.

The Serbs, who already have captured and “ethnically cleansed” more than 70% of Bosnia, claim that Muslim-led government forces have failed to fully retreat from a demilitarized zone on Mt. Igman, a strategic high ground southwest of Sarajevo.

*

The Bosnian government’s delegate to the talks has in turn accused the Serbs of trying to widen the DMZ to further push back the capital’s defenders.

Bosnian President Alija Izetbegovic has warned the U.N. special envoy for the Balkans, Yasushi Akashi, that the continued Serbian assaults on the northwestern Bihac pocket are jeopardizing the Carter cease-fire. Although Bosnian Serbs have ceased shelling the Muslim enclave in accordance with the truce, their Serbian allies in Croatia are not signatories to the deal mediated by Carter and have continued to pound the region with heavy artillery.

The former President’s cease-fire accord was followed by a U.N.-mediated agreement by both sides to halt all hostile actions for four months so peace talks could resume toward an overall settlement of the 33-month-old conflict.

U.N. spokesman Alexander Ivanko has accused both rebel Serbs and the government of foot-dragging in implementation of the cease-fire.

More on Bosnia

* Look to the TimesLink on-line service for a special package of background articles on the origins of the Yugoslav civil war. Sign on and check the Special Reports section of Nation & World.

Details on Times electronic services, A8