There are reports from northern Mozambique that 12 people have died, including several children, when a boat sank in the bay of Pemba.
Thirty-five people survived after swimming ashore on Wednesday.
But they were then apprehended by the police on suspicion that they could be recruits to an Islamist militant group that has been mounting attacks in Cabo Delgado province.
A new report by the UN says displacement of Mozambique's civilian population has risen rapidly in recent months as the jihadists have stepped up their attacks.
More than 200,000 people - most of them women and children - have been forced to flee their homes since the insurgency began in 2017.
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