WAR IN THE BALKANS: THE RISKS TO THE REGION: Alliance and Serbs step up aggression

DESPITE THE furore over who was to blame for the slaughter of civilians in southern Kosovo, Nato stepped up its bombing of Yugoslavia yesterday amid evidence that President Slobodan Milosevic has begun a merciless new push to drive ethnic Albanians from the province.

In Brussels, alliance spokesmen threw little light on the circumstance of Thursday's carnage near Djakovica, saying Nato would accept responsibility only for an attack north of the town. They appeared to deny that allied planes had caused the slaughter on the road south of the town, in which the Serbs say 64 ethnic Albanians died, some of them literally blown to pieces.

But as the doubt and confusion last night swirled over Djakovica, other things were crystal clear - that the war is escalating, that Kosovo's desperate humanitarian crisis is deepening further, and the risk of the conflict spreading into other countries is becoming ever more apparent.

According to the United Nations High Commission for Refugees, a further 100,000 refugees are on the way to the Macedonian border, including 50,000 from the Gnjilane region in southern Kosovo. In addition, 5,000 people crossed over into Albania yesterday, as reports multiplied of Serb forces systematically emptying towns and villages of their populations and laying waste to the land.

If the figures are remotely accurate, it will mean that a third of the ethnic Albanian population have been driven from the province, apart from the unknown numbers still within it, caught between intensifying bombardment from the air and ethnic cleansing on the ground.

Among planners in Nato capitals the urgency is growing. In Washington, the Pentagon announced it was considering calling up 33,000 reservists, while George Robertson, the Defence Secretary, inched closer to sending Nato ground troops to drive the Serbs from Kosovo by force. Officially, such a move is not on the table, but Mr Robertson left the option open, saying that plans "must be kept under review".

Meanwhile, Nato is stepping up the aerial pounding, hitting a range of targets in and around Belgrade yesterday, as well as in Montenegro, Serbia's junior and sole remaining sister republic in the Yugoslav Federation. Allied warplanes had "one of the best nights yet", according to Jamie Shea, the Nato spokesman, claiming hits on tanks, MiG fighters, artillery and anti-aircraft installations.

Nato officials insist that the allied hammering of Serb positions, disrupting fuel supplies and communications, was helping the lightly armed Kosovo Liberation Army (KLA) guerrillas step up their marauding against Milosevic forces.

In Montenegro, however, attacks on Yugoslav army and naval sites have only increased fears that the republic, relatively sympathetic to the West, could fall prey to a coup by Yugoslav army officers and pro-Belgrade politicians, which could unleash a civil war.

Appealing for an immediate end to the fighting, Milo Djukanovic, Montenegro's President, warned that the war was spinning out of control. Though he dismissed the idea of a coup as "not feasible", he spoke grimly of a wider Balkan conflagration: there was "an objective danger the Kosovo fire and blood could engulf not just Yugoslavia but the entire region". If civil war did break out in Montenegro, "it would be more tragic and worse than anything ... in this area".

As if to underline his warning, Serb and Albanian forces exchanged fire for five hours across the frontier near the north Albanian village of Bajram Curri. Serb soldiers had tried to cross the border, but had been pushed back, an Albanian statement said. Analysts fear a generalised war between Serbs and Albanians, sucking in Montenegro and Macedonia too.

Further afield in the Balkans, the conviction is growing that only after Mr Milosevic's removal from power can stability return to south-eastern Europe. Urging the opening of a ground campaign, the Croatian Deputy Prime Minister, Borislav Skegro, declared that "keeping Milosevic in power does not solve anything" - a sentiment echoed by his Bulgarian opposite number Alexander Bozhkov at a conference yesterday in London.

On the diplomatic front, movement has come to a virtual standstill. Mr Milosevic did meet the ethnic Albanian political leader, Ibrahim Rugova, yesterday. But the influence of Mr Rugova, who advocated a non-violent solution to the crisis, is now close to zero.