Elections are being held in five African countries, while Senegal is holding a referendum on reducing presidential terms.

A presidential run-off is going ahead in Niger even though the opposition candidate is in a French hospital.

In Tanzania's semi-autonomous islands of Zanzibar, the presidential election is being re-run after it was cancelled due to irregularities last October.

Elections are also being held in Benin, Cape Verde and Congo-Brazzaville.

The opposition in Niger has called for a boycott alleging fraud.

President Muhamadou Issoufou is expected to win a second term in the vote against former prime minister and parliamentary speaker Hama Amadou.

Mr Amadou was jailed in November on baby-trafficking charges, which he denies. He was flown to Paris last week for medical treatment.

His medical condition is unclear, but his health reportedly deteriorated in prison.

One of the world's poorest countries, Niger faces a growing jihadist threat and was attacked by militants from al-Qaeda and Boko Haram on Thursday.

In February's first round, Mr Issoufou got 48% of the vote while Mr Amadou came second with 17%.

Security is tight in Zanzibar after violent protests over recent elections.

The BBC's Tulanana Bohela reports that there are not many voters in the polling stations she has visited.

The opposition Civic United Front (CUF) has urged its supporters to boycott the poll.

October's election was cancelled after CUF candidate Seif Sharif Hamad declared himself the winner before results were officially announced.

CUF says the annulment was because it had won, while the electoral commission said there had been widespread fraud.