A prominent Cambodian labour leader who was affiliated with the country's main opposition party has been shot dead in the capital, Phnom Penh.
Chea Vichea was one of Cambodia's best-known campaigners
Witnesses said the president of the Cambodian Free Trade Union of Workers, Chea Vichea, was shot at close range.
He helped to organise unions at garment factories and had close ties to the opposition Sam Rainsy Party (SRP).
The motive for the attack is not yet clear but it is the latest in a series of suspected political killings.
A Cambodian government spokesman, whilst condemning the murder, told the BBC the government he did not think the murder was politically motivated but more likely the result of a personal dispute.
A BBC correspondent says this view may be greeted with some scepticism.
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At least three members of the Sam Rainsy Party have been killed in recent weeks.
Boun Maung Ung, a spokesman for the party, said that after the recent election campaign Chea Vichea had received a death threat delivered via a text message on his mobile phone.
But he had had so many threats, according to the opposition spokesman, that he had become used to them and rarely slept in the same location twice.
The current violence is being described as the worst since the 1998 elections, our correspondent says.
Chea Vichea's murder has been described as a loss to the country and its workers.
He and the labour union he led are credited with helping to transform conditions within the garment industry in Cambodia for the more than 200,000 workers it employs.
Chea Vichea was a prominent campaigner, known for his hard bargaining with factory owners and the government.
The opposition has warned that the murder of the labour leader is likely to cast a shadow over negotiations currently under way to form a government.
Although elections were held six months ago, the parties needed to form a coalition to lead the country have been unable to agree on a power-sharing arrangement - in effect consigning Cambodia to a state of political limbo.