Four men have been imprisoned for life after being convicted of rape in Nigeria's northern state of Jigawa.

The state's high court in the town of Birnin-Kudu found them guilty of raping four girls in separate cases.

In a statement, the state justice ministry says two pupils - both eight-year-olds - were attacked while returning from primary schools in separate incidents by the convicts.

The victims in the other cases were aged six and 12.

Some of the convicts had denied the charges levelled against them.

But a spokesperson for the justice ministry, Zainab Baba Santali, says medical reports were part of the evidence presented by prosecutors to the judge to prove what happened.

The convicted rapists have the right to appeal against the judgements.

Campaigners have been decrying increasing cases of rape and low rates of punishment for perpetrators in Nigeria - and pushing for more drastic measures to tackle the problem described by some as an epidemic.