Mr Fujimori has been in Japan since Friday

Mr Paniagua told a news conference in Lima that the president, who was last seen in Japan, had submitted his resignation in a letter to him.

He said he would make its contents known on Tuesday and said that a debate on the presidential succession would be held then.

On Sunday, President Fujimori - embroiled in a corruption row - announced from Tokyo that he would leave office within 48 hours, sparking uncertainty about who would succeed him.

I submit to you, Mr President of Congress, my formal resignation as president of the republic

Alberto Fujimori

The ruling party, Peru 2000, says that the second Vice-President, Ricardo Marquez, should lead the country until 28 July, when the winner of elections due to be held in April takes office.

But the opposition objects: it wants Mr Paniagua to take over instead - and Mr Paniagua himself has not ruled this out.

Peru's main opposition leader, Alejandro Toledo - who has cut short a visit to Spain to return to Peru - has suggested a third option, namely that the country be led by an interim council of eminent figures.

Possible successors

First vice-president - but he has resigned Second vice-president - but the opposition objects Speaker of Congress - proposed by opposition Interim council - proposed by Alejandro Toledo

Under Peru's consititution, the first vice-president should take over - but he resigned last month after a disagreement with Mr Fujimori.

The United States has now stepped into the debate.

A delegation from the US State Department arrived here on Sunday night and has been holding a series of talks with government and opposition leaders.

Fujimori's future uncertain

It is not known when - or whether - Mr Fujimori himself will return to Peru from Japan, his country of descent.

Fujimori downfall file

May 2000: Re-elected third term amid vote-rigging claims 14 Sept: Montesinos scandal breaks 16 Sept: Fujimori announces new elections 23 Oct: Montesinos returns from exile 16 Nov: Opposition takes control of Congress 17 Nov: Fujimori arrives Japan 20 Nov: Fujimori resigns

According to Sunday's statement, he decided to step down after the opposition gained control of Congress last week for the first time in eight years.

But the president has been beset by rumours that he is seeking political asylum since he left the country last week.

Political and financial scandals have been swirling around him ever since his shadowy former spy chief, Vladimiro Montesinos, was caught on film trying to bribe an opposition politician two months ago.

As a result, Mr Fujimori said he would quit four years early, and called the April elections.

All parties have called for President Fujimori to return to Lima and face up to the consequences of his decision.

'Moral incapacity'

Mr Fujimori's own ministers have been among the most outspoken in this respect, saying they feel betrayed by the president's announcement.

Marquez: The oppostion don't want him to head transition

On Sunday the whole cabinet resigned in protest, but it said it would stay on until Mr Marquez formed a new cabinet.

Legislators, however, are expected to demand that Mr Marquez step down.

Opposition lawmakers also say they will not accept Mr Fujimori's resignation and that instead they will declare the presidency vacant due to Mr Fujimori's "moral incapacity".

Despite fears in recent weeks of a possible military coup instigated by Mr Montesinos, the Peruvian military has sworn to abide by the constitution, and to respect any political changes made after Mr Fujimori's departure.