COLOMBO: International rights groups Tuesday criticised the Sri Lankan government for a clampdown on opponents after last week's election and condemned the detention of suspected Tamil rebels.

Amnesty International said pressure on opposition parties has been mounting since President Mahinda Rajapakse was re-elected on January 26, defeating his former army chief Sarath Fonseka.

"Victory against the Tamil Tigers followed by a historic election should have ended political repression in Sri Lanka, but instead we have seen a serious clampdown on freedom of expression," said Amnesty's deputy director for Asia-Pacific Madhu Malhotra.

Amnesty cited the post-poll arrests of opposition supporters and journalists, death threats against several prominent newspaper editors and the harassment of trade unionists.

A pro-opposition newspaper was raided, several websites supporting Fonseka were blocked while Prageeth Eknaligoda, who wrote for the Lanka e-news website, disappeared on his way home from work two days before the election.

Sri Lankan journalists have given Amnesty a list of 56 of their colleagues who face serious threats, including some attached to state-run media organisations.

The independent Centre for Monitoring Election Violence reported more than 85 post-election incidents, including two murders and several assaults.

"Threats, beatings and arrests mean that Sri Lankan human rights activists live in fear of the consequences of expressing their political opinions," said Malhotra.

The government has accused Fonseka and his supporters of plotting a coup and on Monday sacked a dozen senior military officers whom the defence ministry said were a "direct threat to national security".

Amnesty said the government has also detained 13 former military officials supporting Fonseka.

"President Rajapaksa?s government has to show that it will now try to deal with the human rights violations that have plagued Sri Lanka, instead of using the post-election period to launch a new crackdown," Malhotra said.

Human Rights Watch (HRW) urged Sri Lanka to end its indefinite detention of more than 11,000 people suspected of having links to the Tamil Tiger rebels, who were finally defeated in May last year.

The government said those in detention had surrendered when some 300,000 ethnic minority Tamils were displaced during the final weeks of the decades-long conflict.

The lack of transparency and information about the detainees raised concerns about possible torture or mistreatment in custody, HRW said.

"The government has been keeping 11,000 people in a legal limbo for months," said Brad Adams, Asia director at HRW. "It?s time to identify who presents a genuine security threat and to release the rest."