In his remarks, Ambassador Andreas Zobel "has obviously interfered in Serbia's internal affairs," the government said in a statement.

"Ambassador Zobel has, in many ways, questioned the territorial integrity of Serbia and the inviolability of its recognised international borders," the statement continued.

Speaking at a public debate in Belgrade on Wednesday, Zobel said the sensitive issue of Kosovo's status should be solved as soon as possible by granting an internationally-supervised independence to the southern Serbian province.

Ambassador's remarks in line with UN mediator's

That is in line with recommendations made by United Nations chief mediator Martii Ahtisaari for the future status of the Albanian-majority province.

His plan has already been endorsed by Kosovo Albanians, the European Union and the United States but is strongly opposed by Moscow and Belgrade, which has instead suggested that the province be granted autonomy within Serbian borders.

If the Kosovo issue was not solved as suggested, "the problems could reappear in Vojvodina (a northern Serbian province with a multi-ethnic population) and Sandzak," a southwestern Serbian region with a strong Muslim population, Zobel was quoted as saying by private radio B92.

Belgrade call on Berlin for clarification

The Serbian government said it expected "the German government to clarify whether Ambassador Zobel has expressed the official stance of his government."

Serbian President Boris Tadic also sent a protest note to the Germany's foreign ministry, and his office said German President Horst Kohler would receive a similar note.

The German embassy in Belgrade has meanwhile denied that Zobel warned that Vojvodina's future might be on the line, according to a statement quoted by the Beta news agency.

The ambassador himself apologised at a brief press conference late Thursday "for remarks that might have been incorrectly understood," B92 reported.

Though legally a Serbian province, Kosovo has been run by a United Nations mission since mid-1999, when a NATO bombing campaign ended the Serbian forces' crackdown on the independence-seeking ethnic Albanian population.