COLOMBO (AFP) - A Sri Lankan court on Monday banned the former president's brother, Mr Gotabhaya Rajapakse, from leaving the country as police probe private arsenals set up during the previous regime's decade in power.

A magistrate in the southern port city of Galle impounded former powerful defence secretary Rajapakse's passport along with those of three others, the police said in a statement.

"Police investigating the Avant-Garde Security Service floating armoury case sought and secured a ban on their travel abroad," the statement said, naming the four individuals involved.

Shortly after former president Mahinda Rajapakse was defeated at the Jan 8 elections, partly on corruption and cronyism claims, the police in Galle found a ship carrying more than 3,000 automatic weapons, including machine guns.

Investigators have been trying to locate thousands of weapons they say have disappeared from the inventories of the island's security forces and are thought to have been transferred to individuals.

Avant-Garde Security Service has said its legally obtained armoury had been authorised by Gotabhaya Rajapakse to enable the private company to carry out armed escorts of commercial ships.

The new government of President Maithripala Sirisena insists Mr Rajapakse did not have the legal authority to approve such private hauls.

A police source said the former defence secretary has been questioned in Colombo as part of the ongoing investigation and the travel ban was sought because they need to interview him further.

The former president's brothers and other family members held key positions in the previous government. Mr Mahinda Rajapakse's younger brother Basil, who had been economic development minister, left the island soon after the president's defeat.