Seripisut yesterday questioned the man personally and said he disbelieved his claim that the killings had been the result of a robbery gone wrong.

Tatiana Tsimfer, 30, and Liubov Svirkova, 25, were shot dead around dawn on February 24 as they sat in chairs on Jomtien Beach in Pattaya.

Seripisut said Anuchit Lamlert, 24, was the killer. He was arrested on Thursday night. However, Seripisut was convinced that the suspect had not worked alone and that his motive had not been robbery.

He was suspicions of Anuchit's claim because the victims had no valuables on them at the time except for a mobile telephone. The pair had gone to the beach for an early-morning swim.

"Police have arrested the suspect, but I am not satisfied. I believe there must be a motive," he said.

Pattaya police will continue to search for accomplices, and Seripisut said he did not want a "scapegoat".

On Thursday police recovered the murder weapon, a Chinese-made 9mm Norinco pistol.

Anuchit told police he had attempted to rob the women but shot them when they screamed for help.

Police Second Region commissioner and the senior officer investigating the killings, Lt-General Assawin Khwanmueng, said yesterday a Bt550,000 reward had been paid.

Anuchit has been denied bail.