Foreigners seeking to wed Sri Lankans will need security clearances from the defence ministry, under new regulations that were met with scorn and ridicule by the opposition.

The new rules -- seen by AFP on Monday -- will require foreigners from next week to get a clean bill of health and a security check before their nuptials, with registrar general W.M. Weerasekara attributing the policy to "national security" concerns.

"We have seen some foreigners wanting to marry Sri Lankans here with ulterior motives like engaging in drug trafficking and money laundering," Weerasekara told the local Sunday Times newspaper.

The new regulations have prompted scorn from opposition lawmakers who pointed out that several members of the ruling family are dual nationals.

"How about security clearance for foreign nationals to hold cabinet ministerial portfolios...?" legislator Shanakiyan Rasamanickam tweeted.

Sri Lankan President Gotabaya Rajapaksa held US citizenship until two years ago. After coming to power, he scrapped a constitutional provision that barred dual citizens from contesting elections.

His brother Basil, the finance minister, remains a dual citizen of the United States and Sri Lanka.