PHNOM PENH (Reuters) - Cambodian Prime Minister Hun Sen on Wednesday renewed his criticism of the United States, a week after a leading opposition figure fled the country over fears of a widening crackdown on government critics ahead of next year s election. Hun Sen, who has ruled Cambodia for more than 30 years and shows no sign of wanting to relinquish power, has forced the closure of several English-language media and jailed government critics, including opposition leader Kem Sokha. Bombs recently discovered at nine sites in southeastern Svay Rieng province had been dropped by the United States during the Vietnam war, Hun Sen said in a speech to workers at garment factories that export most of their output to the U.S.  These bombs dropped on Cambodia belong to the United States,  Hun Sen said in his latest comments in a growing row over his accusations that American agents conspired with Kem Sokha to overthrow the government. Hun Sen accused the United States of double standards, saying it was critical of his handling of Kem Sokha s case but had shown no respect for human rights in Cambodia when it dropped the bombs. Cambodia ranks among the world s nations most littered with unexploded ordnance, says the Mines Advisory Group, which helps find and destroy unexploded devices that kill and injure an average of two Cambodians each week.  The U.S. Embassy in Phnom Penh did not immediately reply to a Reuters request for comment on the Wednesday remarks. Last week the government filed a lawsuit demanding the dissolution of the opposition Cambodia National Rescue Party (CNRP), a move that would help Hun Sen extend his rule at the election. Other parties were ready to replace the CNRP if it was dissolved, Hun Sen said on Wednesday, adding,  If one party is dissolved, five other parties will replace it.  Western countries have condemned Kem Sokha s arrest for treason and have questioned whether the election can be fair, following the crackdown on opposition leaders, activists and journalists. U.S. Ambassador to Cambodia William Heidt last month rejected government accusations of U.S. interference and urged the release of Kem Sokha, who faces 30 years in jail if convicted. Half of Cambodia s opposition MPs have fled, including outspoken deputy leader Mu Sochua, who left last week.  Hun Sen, a former Khmer Rouge commander who defected from the genocidal group and helped drive it from power in 1979, is allied to China, and Beijing says it supports the Cambodian government s efforts to maintain national security. 