The abductors of an American United Nations official, kidnapped in Pakistan's Balochistan province in February, have threatened to kill him if their demands, including the release of thousands of political prisoners, were not met within the next four days.

The Balochistan Liberation United Front, which abducted UN High Commissioner for Refugees official John Solecki after killing his driver on February 2, listed its demands in a letter sent to a news agency in the southwestern city of Quetta on Sunday night.

The BLUF demanded the release of 141 Baloch women prisoners and thousands of political prisoners who were, it claimed, being held in different jails across Pakistan.

It warned that it would kill Solecki if these demands were not met within four days.

Officials in Quetta told reporters that the government of Balochistan province had established contacts with tribal and political leaders to negotiate Solecki's release.

The BLUF had earlier said it was providing medical facilities to the ailing Solecki, who heads the UNHCR office in Balochistan province. It has also spurned the UN's offer for Solecki's abductors to make direct contact for negotiations on his release.

However, officials have dismissed the BLUF's claims about Baloch women and political activists being detained by security agencies.