ZAGREB, CROATIA — CHILDREN'S voices and the whispers of nurses fill the air. More than 400 young faces stare out from makeshift bunks in the cramped bomb shelter of Zagreb Children's Hospital, just hours after a Serb rocket killed one and wounded five others here Wednesday.
With a second day of retaliatory rebel Serb rocket attacks on the Croatian capital, Zagreb's basements are turning into shelters and attention is shifting to the Serb-held south. Speculation about the attackers' motives, hopes of a split in the rebel Serb leadership, and calls for Croat retaliation are mounting.
''They should be drowned in the sea with all these weapons,'' says Zelko Sic, comforting his 11-year-old daughter in the shelter.
The second rocket attack -- which also struck an annex to the Academy of Dramatic Arts -- killed one and wounded about a dozen others from the Danube Ballet Company. After an attack on Tuesday that left five dead and 121 wounded, Western diplomats now say a more radical faction in the Croatian Serb leadership may be trying to draw Croatia into an all-out war.
Diplomats say the next several days are crucial. If the Serb attacks continue, violating a cease-fire negotiated by United Nations officials late Wednesday, war will quickly ensue. A renewed war could place UN peacekeepers in the line of fire and prompt a dangerous UN pullout, assisted by US troops.
''So far, the Croats have said they will exercise restraint,'' warns a senior Western diplomat, ''but obviously at some point a government cannot accept having missiles land in its capital and kill its people.''
Faced with the successful Croatian military seizure of Western Slavonia, the most vulnerable of four Croatian Serb strongholds this week, nationalist Croatian Serb ''president'' Milan Martic and Croatian Serb military commander Gen. Milan Celeketic may fear a gradual erosion of their political, military, and economic position.
''I think that basically what's going on is that there's a power struggle in [the Serbs' self-proclaimed capital of] Knin,'' says a senior Western diplomat. ''The rejectionists [of a diplomatic solution] ... are trying to provoke a wider war.''
Diplomats say they believe a majority of deputies in the Croatian Serbs' self-declared assembly, led by moderate prime minister Borislav Mikelic and backed by Serbian President Slobodan Milosevic, may oppose the rocket attacks.
The renewed talks of a split reflect the West's continuing and much-criticized strategy of largely relying on Mr. Milosevic -- who critics say is responsible for launching the violent breakup of the former Yugoslavia and cannot be trusted -- to bring peace to the region by reining in rebel Serb leaders in Croatia and Bosnia.
Critics warn that the West is overestimating Milosevic's power and angering Croatian Serb leaders by calling for their overthrow. The political situation in Knin remains murky. The Croat offensive may actually have strengthened the hand of nationalists.
They also point to Bosnia, where an apparent split between Milosevic and Bosnian Serb leader Radovan Karadzic led the Serbian leader to officially cut off aid to the Bosnian Serbs last August. But Mr. Karadzic remains firmly in power, and critics say large amounts of weapons and fuel are still flowing to the Bosnian Serbs. ''We have this new cease-fire, we'll see,'' the senior diplomat says. ''It's totally unpredictable.''
Croatian officials, enjoying their largest military victory since they claimed independence from Yugoslavia in 1991, are talking tough and are well-positioned to strike back at the Serbs.
''If they repeat the attacks again,'' Croatian President Franjo Tudjman warned in an address to the nation Wednesday night, ''then Croatia will respond with decisiveness to prevent any further terrorism.''
Croatia appears to have followed a clear, long-term strategy that led to the successful offensive. Despite being theoretically under a UN arms embargo, the Croatian Army now boasts nearly as many tanks and artillery as Croatian Serb forces and enjoys a nearly 2-to-1 manpower advantage.
Less-publicized recent operations by the Croatian Army in Croatia and the Croat militia in Bosnia have resulted in their artillery now being within range of Knin.
Western diplomats and UN officials say they were impressed by the conduct of the Croatian military in the offensive. ''The Serbs didn't expect such a big operation; it was pulled off on three sides,'' says a UN military observer in Western Slavonia. ''The movements of the Croats were very swift.''
The taking of Western Slavonia, the largest loss of Serb territory loss in all of the former Yugoslavia, also calls into question whether undermanned and poorly supplied Serb forces in Bosnia and Croatia are becoming paper tigers, officials say. The military observer says Croatian Serb resistance quickly collapsed when it became clear that Serb forces in neighboring Bosnia, apparently tied down by a resurgent Bosnian government Army, were not going to aid them.
''They expected that they were going to get a lot of help from the Bosnian Serb army,'' the military observer says. ''When they saw it wasn't happening, they gave up.''
But Croatian Serbs are believed to have enough rockets to continue hitting Zagreb for a long period, and the psychological toll on the city has been heavy. Each Orkan rocket carries 288 bomblets that separate from the rocket and explode in a 30-foot area. Each bomblet contains 420 deadly steel pellets.