Protesters demand all videos be made public

The release of the tapes is expected to coincide with the signing of a political pact to refrain from personal attacks in the run-up to presidential elections set for 8 April.

Political groups tainted by other so-called "Vladivideos" accuse interim President Valentin Paniagua's government of manipulating the release of tapes to favour front-runner Alejandro Toledo's bid for office.

Mr Paniagua has repeatedly denied the accusations.

'Dirty tricks'

The tapes are among hundreds confiscated from Mr Montesinos.

The videos to be released by Congress on Monday are reported to involve the Fujimori-sympathising candidate, Carlos Bolona.

Mr Bolona is reported to be shown discussing a plan to launch personal attacks on some of the candidates who ran against former President Fujimori in last year's elections.

Interim congress speaker, Carlos Ferrero, is also believed to appear in one of the videos. He was Mr Toledo's running mate in the previous election.

Two months before the elections, opinion polls give the centre-left candidate Mr Toledo a commanding lead, but not a majority.

The battle now seems to be for second place and the chance to face Mr Toledo in a run-off.

But the release of videos showing politicians close to the other candidates have sparked concerns the tapes could be used as political weapons.

Mr Montesinos, meanwhile, remains a fugitive, having disappeared in October of last year. He is wanted on charges of arms smuggling, drug trafficking and human rights abuses.