Maldives Vice President Ahmed Adeeb was arrested today in a probe over a speedboat explosion targeting President Abdulla Yameen, a police official told Reuters.

Mr Yameen was unhurt in the September 28 blast in his presidential boat Finifenmaa while he was returning from Saudi Arabia after the haj pilgrimage.

"We have arrested the vice president in relation to the Finifenmaa incident," a police media official told Reuters.

"He is now in police custody in Dhoonidhoo detention centre."

Home minister Umar Naseer in his twitter feed said the charge against the vice president was "high treason".

In recent years, the Maldives has been rocked by political infighting.

Mr Yameen's election has been the subject of drawn-out wrangling.

Security has been tightened in the capital Male amid fears of "turmoil" triggered by the arrest, says the Maldivian newspaper Haveeru.

"By early morning Saturday, lorries loaded with policemen and soldiers were seen on nearly every street," it reports.

Three others were also arrested today - including a former member of Adeeb's security detail and a member of the army's bomb squad, Associated Press news agency reported.

The Maldives Independent website said Mr Adeeb's arrest had "surprised and enthralled many Maldivians".

Mr Adeeb had met Maltese President Marie-Louise Coleiro Preca during a visit to Malta last August where he had presented her with a letter from Mr Yameen.