The Nato F-18 attack aircraft will be based at an American airbase only 70 kilometres from the Yugoslav border - and 270 kilometres from Belgrade.

The planes will be used to step up attacks from the north, while F-15 and F-16s will begin missions from Nato bases in Turkey, flying over Bulgaria.

Hungarian air space and airports have been used since the beginning of the Nato campaign, but these will be the first planes to take-off from Hungarian soil on attacking missions.

While the numbers of planes involved represent only a small part of the arsenal that Nato has deployed through the region, they're clearly intended to increase the sense of seige inside Yugoslavia.

Public concern

Hungarian public opinion remains largely supportive of the air campaign, but polls suggest a clear majority are against the attacks taking place from Hungarian territory.

There is also growing concern about the fate of the large Hungarian population in the province of Vojvodina in northern Serbia.

Hungarian leaders are vocal in their support for the air campaign, but they have also tried not to provoke Yugoslavia.

The Yugoslav embassy in Budapest remains open and diplomatic contacts continue. On Tuesday two Serbian prisoners of war were handed back across the Hungarian-Yugoslav border.