"All kinds of right-hand drive vehicles will be seized and kept as state property if found in traffic in public after the deadline," a letter from the Transport Ministry warned.

The ban follows years of warnings for car-owners to have their steering columns changed from the right to left.

It aims to stem the tide of smuggled and stolen vehicles from neighbouring Thailand, which has right-hand drive steering for Thai roads where drivers keep to the left.

In Cambodia, a former French protectorate, motorists drive on the right-hand side.

Costly

News agencies reported that many right-hand drive cars were still on Cambodia's roads on Monday.

The government said that it had not began to implement the crack down yet because of the New Year's holiday.

Cars that were not retrieved by owners would become state property, he said.

The price of changing the steering column - ranging from $600 to $2,000 - is costly in a country where the annual income is less than $1,000.

Many Cambodians are said to be unhappy with the ruling.

"A demonstration will be held if the government wants to confiscate our cars," taxi driver Ngeth Chay told AFP.