Muslim separatists in the southern Philippines have postponed a second round of peace talks with the government, which were due to begin on Monday.

Mohagher Iqbal, spokesman for the Moro Islamic Liberation Front (MILF), said the decision was taken after government troops attacked one of their main bases on Mindanao island, 800km (500 miles) south of Manila.

"We wanted clarification of the official position of the government - whether they are willing to find a lasting solution to the problem through negotiations, or whether they are now resorting to full military operations against us," he said.

At least 25 people were killed in the fighting, which broke out in a mountainous area near the base a week ago.

The clashes erupted on Wednesday after 3,000 soldiers launched an offensive on the MILF's Camp Omar in Maguindanao province.

The rebels responded by seizing two villages on the border of Maguindanao and North Cotabato province, trapping hundreds of civilians.

The fighting left at least 23 rebels and two soldiers killed. Reports say 22 soldiers and six civilians were wounded in the fighting.

Accusations exchanged

Each side has accused the other of breaking a tenuous ceasefire by instigating the fighting.

The latest session of peace talks was scheduled to take place in Cotabato city.

Defence Secretary Orlando Mercado said the government would continue the search for a peaceful settlement.

But he said the talks would resume only when "a more conducive environment" prevailed.

The rebels are fighting for an independent Islamic state in the island of Mindanao.

The mainstream Moro National Liberation Front (MNLF) signed a peace deal with Manila in 1996, but the MILF - a breakaway faction - has continued the struggle.

On Saturday, Philippines President Joseph Estrada stressed that the peace negotiations would not touch on the MILF's seccessionist demand, but would focus on reviving economic growth in the south.

"There is only one country, one government and one constitution," he declared, adding that negotiators had been given until June to work out a deal.