Memorial for victims of a deadly grenade attack, in Phnom Penh

Buddhist monks pay respect in front of a memorial for victims of a deadly grenade attack, in Phnom Penh March 30, 2010. Members of Cambodia's opposition Sam Rainsy Party on Tuesday mark the 13th anniversary of an attack on supporters of Sam Rainsy, during which 16 people were killed and another 150 injured. An FBI investigation concluded that Cambodian government officials were responsible for the attack, according to the Human Rights Watch last year. REUTERS/Chor Sokunthea

Buddhist monks pay respect in front of a memorial for victims of a deadly grenade attack, in Phnom Penh March 30, 2010. Members of Cambodia's opposition Sam Rainsy Party on Tuesday mark the 13th anniversary of an attack on supporters of Sam Rainsy, during which 16 people were killed and another 150 injured. An FBI investigation concluded that Cambodian government officials were responsible for the attack, according to the Human Rights Watch last year. REUTERS/Chor Sokunthea

Buddhist monks pay respect in front of a memorial for victims of a deadly grenade attack, in Phnom Penh March 30, 2010. Members of Cambodia's opposition Sam Rainsy Party on Tuesday mark the 13th anniversary of an attack on supporters of Sam Rainsy, during which 16 people were killed and another 150 injured. An FBI investigation concluded that Cambodian government officials were responsible for the attack, according to the Human Rights Watch last year. REUTERS/Chor Sokunthea

Portraits of a grenade attack victims are seen at a memorial, in Phnom Penh March 30, 2010. Members of Cambodia's opposition Sam Rainsy Party on Tuesday mark the 13th anniversary of an attack on supporters of Sam Rainsy, during which 16 people were killed and another 150 injured. An FBI investigation concluded that Cambodian government officials were responsible for the attack, according to the Human Rights Watch last year. REUTERS/Chor Sokunthea

The relative of a grenade attack victim pays respects in front of a memorial, in Phnom Penh March 30, 2010. Members of Cambodia's opposition Sam Rainsy Party on Tuesday mark the 13th anniversary of an attack on supporters of Sam Rainsy, during which 16 people were killed and another 150 injured. An FBI investigation concluded that Cambodian government officials were responsible for the attack, according to the Human Rights Watch last year. REUTERS/Chor Sokunthea

The portrait of a grenade attack victim is seen at a memorial, in Phnom Penh March 30, 2010. Members of Cambodia's opposition Sam Rainsy Party on Tuesday mark the 13th anniversary of an attack on supporters of Sam Rainsy, during which 16 people were killed and another 150 injured. An FBI investigation concluded that Cambodian government officials were responsible for the attack, according to the Human Rights Watch last year. REUTERS/Chor Sokunthea

Buddhist monks pay respect in front of a memorial for victims of a deadly grenade attack, in Phnom Penh March 30, 2010. Members of Cambodia's opposition Sam Rainsy Party on Tuesday mark the 13th anniversary of an attack on supporters of Sam Rainsy, during which 16 people were killed and another 150 injured. An FBI investigation concluded that Cambodian government officials were responsible for the attack, according to the Human Rights Watch last year. REUTERS/Chor Sokunthea