NOUAKCHOTT (Reuters) - Three protesters have died in detention in Mauritania, the interior ministry said on Tuesday, after security forces made mass arrests in the town of Kaedi to contain unrest in the wake of the West African country's presidential election.

The ministry said protests turned violent in the southern town near the border with Senegal late on Monday, prompting security forces to confront demonstrators and detain certain groups.

"Unfortunately, under these circumstances, three demonstrators died. Two of them died in the detention facility in the presence of their fellow detainees, while the third died later in the hospital," it said in a statement.

It did not give further details on their cause of death or the number of people detained, but said an investigation would be carried out.

The unrest followed an announcement on Sunday that President Mohamed Ould Ghazouani had won a second term, according to provisional results that his main rival, anti-slavery activist Biram Dah Abeid, rejected over alleged irregularities.

On Tuesday, the authorities restricted access to mobile internet "amid protests rejecting the results of this weekend's presidential elections", internet monitor Netblocks said.

Opposition concerns about the credibility of the electoral process sparked small-scale protests after the 2019 presidential vote also.

(Reporting by Kissima Diagana; writing by Alessandra Prentice; editing by Mark Heinrich)