LONDON (Reuters) - The lead singer of rock group Lostprophets was sentenced on Wednesday to 35 years in a British jail for child sex offences, and police said they were investigating whether he committed similar crimes in Germany and the United States.

Ian Watkins, 36, pleaded guilty to 13 counts of child sex offences at Cardiff Crown Court in Wales last month. He was charged along with two mothers of the abused children, who also pleaded guilty.

"The investigation uncovered the most disturbing child abuse evidence I have seen in my 28 years as a police officer," Detective Chief Inspector Peter Doyle, Senior Investigating Officer for South Wales Police, said in a statement.

"There are also investigations being conducted by other police forces around the world including Germany and the United States," he said.

Lostprophets, a Welsh group which has sold more than 3 million records worldwide, broke up in October after Watkins was charged.