"Do not try to put this country hostage for bargaining your power," Hun Sen said, warning that any attempt to stage a civil war will be "cracked down on in just hours."
Hun Sen issued the warning amid a brewing political crisis over the outcome of last July's general election.
The opposition Cambodian National Rescue Party (CNRP) has refused to recognise the outcome of the election, won by the ruling Cambodian People's Party (CPP), on grounds the polls were rigged to ensure a CPP victory.
The opposition has boycotted all parliament sessions and staged mass protests, demanding a serious probe of the election, reform of the National Election Committee, organisation of a new election and Hun Sen's resignation.
Hun Sen said a political settlement should be conducted through negotiation or through the National Assembly.
"It should not be settled by walking in the streets," he said.
The CPP won 68 seats of the total 123-seat National Assembly in last July's general election, while Sam Rainsy's CNRP got the remaining 55 seats.