PHNOM PENH Cambodian police found a home-made bomb near parliament and three grenades near a park in the capital, Phnom Penh, where opposition supporters are to start a mass rally at the weekend in protest at alleged electoral fraud.
A controlled explosion of the bomb on Friday shook nearby buildings, which added to the tension over the contested results of the July 28 general election, won by the party of long-serving Premier Hun Sen, according to the electoral authorities.
"This is aimed at making people scared and to cause instability," National Military Police Spokesman Kheng Tito said, adding the authorities had not identified any suspects.
Small numbers of military police were present on the street on Friday, as they have been for most of the time since the election.
The rally is due to run from Sunday to Tuesday.
The National Election Committee (NEC) says Hun Sen's Cambodian People's Party (CPP) won 68 of the 123 seats in parliament, beating the opposition Cambodia National Rescue Party (CNRP), which took 55.
The CNRP says it won with 63 seats to the CPP's 60 and wants an independent investigation in the results. It has also said it would boycott the new parliament, which is scheduled to convene on September 23.
The Constitutional Council, the country's highest court, which is under the influence of the CPP, has rejected calls for further investigations and said this week that people who failed to respect its decision could face up to a year in prison.
In a move to end the stalemate, King Norodom Sihamoni has invited Hun Sen and CNRP leader Sam Rainsy to a private meeting on Saturday.
"I am optimistic that if they come together, the parties will be able to reconcile their differences," said Ou Virak, president of the Cambodian Center for Human Rights (CCHR).
Hun Sen has been in power for 28 years and had been expected to win the election easily, but the recently merged opposition pulled off a surprise, backed by younger voters wanting more social justice and an end to corruption.
(Reporting by Prak Chan Thul; Editing by Alan Raybould and Nick Macfie)