A government minister in Madagascar has said he swam for 12 hours to safety after his helicopter crashed at sea during a rescue mission.

"It's not my time to die," exhausted Police Minister Serge Gelle said as he recovered on a stretcher.

Two other security officials travelling with him in the helicopter also survived the crash.

The team had been scouting an area in the north-eastern part of the country where a passenger boat had sunk.

At least 39 people died in that accident, officials said on Tuesday.

On Twitter President Andry Rajoelina mourned those who died and also paid tribute to Mr Gelle and the other two officers, who arrived in the seaside town of Mahambo separately.

C’est avec une profonde tristesse que j’ai appris le naufrage d’un navire au large d’Antsiraka et son terrible bilan. Mes pensées vont aux victimes et à leurs proches endeuillés.

Je prie solennellement pour le repos de leurs âmes. pic.twitter.com/nZzJsaYMtL

— Andry Rajoelina (@SE_Rajoelina) December 21, 2021

It is unclear what caused Monday's accident to happen but Mr Gelle, 57, said after the crash he swam from "7:30 last night, until 7:30 this morning," to Mahambo.

He said he had no injuries but added that he was feeling cold.

"I would just like you to broadcast this video for my family to see, my colleagues to see, the government members to see. [I am] alive and well," Mr Gelle told villagers at Mahambo.

Police chief Zafisambatra Ravoavy told news agency AFP that Mr Gelle had used one of the helicopter's seats as a flotation device.

"He has always had great stamina in sport, and he's kept up this rhythm as minister, just like a 30-year-old... he has nerves of steel," Mr Ravoavy said.

Mr Gelle had served in the police for three decades before his August appointment as minister.