COLOMBO (AFP) - A Sri Lankan government crackdown this month on NGOs has sparked claims that President Mahinda Rajapakse, paranoid that he could be toppled, is again attempting to silence critics and tighten his grip on power.

The defence ministry this month banned non-governmental organisations from holding press conferences, awareness campaigns, training for journalists, workshops and disseminating press releases on everything from voter rights to exposing corruption.

The ministry, which has regulated local and foreign NGOs since soon after the end of the island's civil war in 2009, said the order was necessary to stop them operating "beyond their mandate".

But NGO workers, many of whom have long suffered harassment and intimidation in Sri Lanka, said the order was a new crackdown on dissenting voices ahead of possible snap presidential elections.

"The move... came from a government that finds itself a tad shaky as the country prepares for presidential elections," said Bob Dietz, Asia program coordinator for the New York-based Committee to Protect Journalists.

"For all its efforts to silence its critics, the government, with its new move to stifle NGOs, may have instead moved one more step toward irrelevance." Authorities have often accused foreign and local charities of supporting dissidents, and introduced tougher regulations to control them in 2010, a year after troops crushed Tamil rebels and ended decades of ethnic war.

- 'Spooked by USAID' -

A cabinet minister said the administration was rattled by a USAID move to fund a voter awareness program, after independent election monitors warned of malpractices in preparing voter lists for future elections.

The minister said the administration was paranoid about NGOs which it feared would fuel criticism of Rajapakse and his family, leading to its overthrow.

"The government panicked when they heard that USAID was trying to educate voters about their rights," he told AFP on condition of anonymity.

"There are some (in government) who fear a conspiracy to engineer a regime change." There was no immediate comment from USAID.

Senior ruling party officials have said Rajapakse, who has extended his powers since being elected in 2005, was likely to seek reelection at a snap poll early in 2015, two years ahead of schedule.

Rajapakse is popular with the ethnic Sinhalese majority for ending the decades-long war against Tamil rebels fighting for a separate homeland for the Tamil minority.

But his government faces international censure over alleged rights abuses against Tamils in the final months of the conflict, and was accused by the UN's rights chief Navi Pillay last year of growing "increasingly authoritarian".

Authorities routinely block access to popular anti-government websites that have replaced a largely ineffectual political opposition.

This month's ban came after a campaign of intimidation targeting the local chapter of Berlin-based corruption watchdog Transparency International.

Hundreds of pro-government activists stormed a hotel north of Colombo last month where the TI staff were holding a workshop to train local journalists in exposing corruption.

Rights groups have long sought to highlight problems for the media in Sri Lanka, where many journalists practise self-censorship after more than a dozen journalists and media workers were killed in recent years.

- Death threats -

The activists carried placards bearing the photo of local TI spokesman Shan Wijetunga and the word "traitor". Police ordered the workshop to be shutdown, rather than disperse the activists.

"I have also received telephone calls threatening me with death," Wijetunga told AFP. "These calls came from numbers which cannot be traced." About 20 pro-government Buddhist monks stormed another journalism workshop in March in the island's east organised by the US-based Search For Common Ground, forcing its closure.

The US government has expressed concern at the crackdown on NGOs.

"We strongly urge the government of Sri Lanka to allow civil society organisations and NGOs...to operate freely," US State Department spokesperson Jen Psaki said in a statement.

Sri Lanka's influential Bar Association (BASL) feared the ban could soon be extended to other civil society groups, including the association and trade unions.

About 1,420 NGOs have registered with the defence ministry as required, although some have refused on the basis that they were charities operating as private companies.

BASL president Upul Jayasuriya warned the country was headed towards a dictatorship, with the latest crackdown an attempt by Rajapakse's regime to tighten its grip on power.

Two unidentified men on a motorcycle and another in a three-wheeler taxi have been following him around the city since BASL issued a press release condemning the move against NGOs, he said.

"I suspect a link between my issuing the statement and the men following me," Jayasuriya told reporters. "They left only after I raised the alarm and called the police."