By Prak Chan Thul

PHNOM PENH (Reuters) - International powers should keep out of Cambodian domestic politics, Prime Minister Hun Sen warned on Tuesday, as he posed for selfies with supporters and played down tension between his ruling party and the opposition.

An opposition win in an election due in 2018 could tip the country back into civil war, the quixotic Cambodian strong man has warned. Foreign governments have accused him of intimidating his political opponents ahead of the vote.

Those who portrayed the country as experiencing a political crisis were guilty of a "dishonest trick to deceive public opinion," Hun Sen said in the capital, Phnom Penh.

"They must not misconstrue individual mistakes as political issues and put pressure on the courts," he added, in a reference to foreign governments and international institutions.

"That is an insult to people, state institutions and a dangerous adventure for the nation."

Last month, the European parliament threatened to review nearly half a billion dollars of aid to Cambodia if Hun Sen's government continued to harass political opponents. The United Nations and the United States have called for dialogue between the two sides.

Tension has risen in Cambodia as opposition leaders Sam Rainsy and Kem Sokha face legal charges they say have been trumped up by a judiciary in thrall to Hun Sen.

The Cambodian prime minister says if they have committed crimes, they must face the legal consequences.

The opposition says the prime minister has started a campaign against it early, to weaken its campaigning ahead of the election.

At the last vote in 2013, a strong performance by the opposition Cambodia National Rescue Party (CNRP) nearly cost Hun Sen the premiership.

Sokha has spent one month in hiding inside the CNRP headquarters as he seeks to evade arrest, while Rainsy is in self-imposed exile to avoid arrest on charges for which he had previously received a royal pardon.

(Reporting by Prak Chan Thul; Editing by Simon Webb and Clarence Fernandez)