Pakistani Taliban said on Wednesday they would not kill two Chinese engineers and two Pakistanis they have been holding since last week, but they would not release them unless unspecified demands were met.

Two Chinese telecommunication engineers and a Pakistani driver and guard were kidnapped near the Afghan border on Friday when they were returning to a guest house after repairing a telecommunications tower.

A Taliban spokesman said on Tuesday they were holding the four.

A Taliban spokesman in the northwest said the four would be held until Taliban demands were met, although he declined to say what the demands were, adding that the Taliban were awaiting an approach from the government.

"There's no plan to kill them. If the government does not listen to us or contact us, then they'll remain detained," said the militant spokesman, Muslim Khan.

The militants have been pressing for enforcement of hardline Taliban-style rule and have in the past demanded an end to military operations against them and the release of their captured comrades.

The four were abducted in Dir, a mountainous region that borders Afghanistan as well as the Pakistani tribal region of Bajaur and the Swat Valley, where security forces have been fighting al Qaeda and Taliban militants.

The Chinese Foreign Ministry said on Tuesday the government was seeking to clarify what happened.

"We have already asked Pakistan to make every effort in a search and to ensure the safety of the lives of the two individuals," a ministry spokeswoman said.

Militants have targeted Chinese nationals in Pakistan's northwest in the past.

Two Chinese engineers working on a hydro-electric project were kidnapped by militants in October 2004. One of the hostages and a militant commander were killed in a rescue operation.

Such incidents add to worry among foreigners about their security in Pakistan but there has been no rush to leave.

"Everything is OK. We haven't even taken the first step of asking foreign staff to send their families back," said a UN official, who declined to be identified.

But security is tight for staff travelling to the violence-plagued northwest.

"Our foreign staff do travel quite frequently so we inform the government about their travel plans and they provide security," the official said.

Violence has surged in Pakistan, especially in the northwest, in recent weeks after militants suspended talks with a new civilian government in June and vowed attacks across the country.

In response, security forces launched military operations in the Bajaur and Swat regions and the Interior Ministry said this week more than 550 militants, including foreigners, had been killed in recent clashes.

Last week, the government announced a suspension of military operations in the northwest for the Muslim fasting month of Ramadan though a top official said security forces would respond with full force if attacked.