Islamabad - The United Nations Monday made a fresh appeal for the release of its official, John Solecki, who is being held by Baloch separatists in south-west Pakistan, a day after his captors threatened to kill him if the government did not release more than 1,100 prisoners in four days, officials and media reports said.

"We keep appealing for the immediate and safe release of Mr Solecki," said UN spokeswoman Maki Shinohara, while confirming that the world organization had learned about the deadline.

Solecki, the regional chief of the United Nations High Commissioner for Refugees office in Pakistan's south-western Balochistan province, was abducted on February 2 in the provincial capital, Quetta.

A shadowy rebel group, the Baloch Liberation United Front (BLUF), in a letter sent to the local Online news agency late Sunday, said that it was extending the earlier deadline, giving the government four days to free the prisoners.

"We are giving the last deadline for meeting our demands," warned the letter, saying the state institutions should be held responsible if Solecki got killed.

The BLUF also urged Solecki's mother, relatives and friends to ask American and international human rights organizations to play a role in the release of 1,109 people who it said were being held by Pakistan's law enforcement agencies.

Maki said the UN officials were going through the English translation of the letter sent to the media and they were in contact with the Pakistani government on the list of prisoners sent by the abductors.

The separatist group earlier asked the UN to resolve the issue of Balochistan's independence under the Geneva Convention. (dpa)