Cambodia spent $1.22 billion to purchase petroleum from foreign suppliers in the first nine months of this year, a 18 percent rise compared with $1.03 billion it spent during the same period last year, a Commerce Ministry's report showed Monday.

The report said that the country had imported 1.24 million tons of petroleum from January to September this year, up 13 percent from 1.1 million tons at the same period last year.

The rising oil demand was attributed to the growing extent of economy and the increasing number of vehicles. The government predicted that the demand will increase up to 4 million tons a year in coming years.

The country entirely buys oil from Vietnam, Singapore and Thailand as its seabed's oil and gas have not been exploited.

Last year, it spent $1.38 billion to import some 1. 46 million tons of petroleum, the report said.