The young man accused of raping a 12-year-old autistic girl in Songkhla has denied the offence and accused his 16-year-old girlfriend of injuring her young sister with a foreign object.

Pol Col Anurut Im-ab, deputy commander of Songkhla police, said 19-year-old Sanphit Kobbo told police that his girlfriend had penetrated her young sister with a cucumber. Forensic examiners would determine if this was true or not.

Mr Sanphit and his girlfriend were arrested in Hat Yai district on Wednesday afternoon. They had been hunted since August 20, following the suspected rape of the 12-year-old girl and assault and robbery of the 73-year-old grandmother who had raised both the girls.

Pol Col Anurut also said both suspects had admitted to abusing drugs. They were held for interrogation at Sadao police station.

Somboon Sae Lim, the 45-year-old father of the two girls, said doctors at Hat Yai Hospital reported that his youngest daughter's vagina was ruptured. Doctors could not find any trace of sperm because of the excessive bleeding. He did not believe the boyfriend's claim, saying there were no traces of cucumber found at their home in Sadao district, where the crime occurred, or on the girl's body.