A serial child killer and paedophile already in jail in Northern Ireland for three child murders was convicted of murdering a fourth girl Thursday, 30 years after she died.

A jury in the town of Armagh found Scottish-born Robert Black, 64, guilty of murdering Jennifer Cardy, aged nine.

Black denied guilt but did not take the stand to defend himself. He was sentenced to life imprisonment.

He was already serving a minimum 35 years for three murders - which would have seen him freed in 2029 at the earliest.

Cardy's mother Patricia sobbed when the verdict was read out. Outside the court her husband Andy told reporters the couple had prayed for their daughter's killer.

We have had to endure and listen to how Robert Black kidnapped and sexually abused and murdered our daughter. It has been absolutely horrendous and we heard things that, in all honesty, were not even in our imagination, he said.

We pity Robert Black and the awful life he has lived. We prayed for Robert Black before leaving the court.

Police in Britain and further afield in Europe say Black may be responsible for a string of unsolved child murders dating back as far as 1969. He is likely to face further questioning.

Cardy was snatched near her home in the village of Ballinderry, in County Antrim, on August 12 1981 while riding her red bicycle, a birthday present two weeks before.

Her body was found at a roadside dam 15 miles (25 km) away at Hillsborough six days later.

Black first tried to rape a girl when he was 12 and later spent a year in juvenile detention for a sexual attack.

He later admitted having molested up to 40 girls after he got a job as a delivery boy in Glasgow, Scotland, when he was 15.

After an attack in 1990 he was caught and later linked to the three murders.

(Editing by Carmel Crimmins and Richard Meares)