PHNOM PENH - CAMBODIAN authorities have arrested four men on suspicion of planting three bombs around the capital last week, a senior police officer said on Saturday.

Deputy national police commissioner Sok Phal told reporters that one of the four alleged plotters was 44-year-old Som Ek, a dual Cambodian-Thai national who had previously worked as a Cambodian military policeman.

'He (Som Ek) told the police that his bomb plot was to bring attention to the group inside and outside the country, so he could extort money,' Mr Sok Phal said.

'This is just some kind of business just to rob or extort money,' he added.

He said Som Ek had been arrested on Wednesday and told authorities that his group was backed by people outside Cambodia.

The deputy police commissioner gave no further details on the alleged group or other three suspects.

No one was harmed in the bomb plot in which police found three explosive devices on January 2 planted near the Ministry of National Defence and a television station.

Mine clearance personnel destroyed the bombs later that day. -- AFP