Police have arrested two Thai men while expanding the search for two missing Russian siblings in the Pattaya area, using sniffer dogs to look for clues.

Pol Lt Col Prabda Suksuntree, superintendent of Pattaya police station, said on Thursday that officers raided the homes of two suspects known only as "Suea Hoi" and "Phang".

The pair are suspected of helping ex-convict Thana Kerdthong, 43, and Thongchai Srinil, 39, evade arrest by hiding them in a motorcycle sidecar covered with a tarpaulin. They are also suspected of helping bury the dismantled motorcycle belonging to the missing siblings.

Police stopped Suea Hoi while he was riding a motorcycle with a sidecar after leaving his mother's house. He was then taken to Phang's home, where the second suspect was arrested.

Both men denied any involvement, saying they did not know Thana or Mr Thongchai. They are being held at Huai Yai police station.

Investigators have also obtained arrest warrants from the Pattaya Provincial Court for Thana and Mr Thongchai on charges of jointly committing theft at night using a vehicle or, alternatively, receiving stolen property, as investigators said the evidence currently links them only to the stolen motorcycle.

Police detain Phang, left, and Suea Hoi, over allegations they helped suspects evade capture and bury the missing Russian siblings' motorcycle.

The search entered its fifth day on Thursday after Diana Nazimova, 22, and her brother Ro- man Nazimov, 17, vanished early Sunday morning along with their black-and-grey Honda motorcycle.

Reports say they were last seen leaving their house at the Bristol Park Pattaya housing estate in tambon Huai Yai.

On Wednesday morning, police recovered the dismantled motorcycle, with its parts buried about 500 metres from the house of one of Thana's close relatives in tambon Huai Yai.

Provincial Police Region 2 investi- gative commander Pol Maj Gen Kiatisak Sathong-oi led police, district officials and two sniffer dogs in a search operation around Khao Chi Chan.

Police teams searched suspected locations in tambon Na Jomtien of Sattahip district and tambon Huai Yai of Bang Lamung district after reconstructing possible movements of the suspects and identifying places where evidence or bodies might have been concealed.

The dogs were given clothing belonging to the missing siblings before searching ponds and an abandoned building near Na Jomtien. Investigators also checked reports that the pair may have travelled to Chanthaburi but found no evidence they had left Chon Buri.

Police said CCTV footage showed Thana and Mr Thongchai riding a motorcycle along Highway 1008 on July 26 after apparently leaving the house of Mr Thongchai's sister, where they were believed to have showered and changed clothes before returning to Huai Yai.

Thana's 74-year-old aunt appealed for him to surrender. She said he had been released from prison less than two months ago and last visited her on Monday before leaving abruptly after receiving a phone call.