South Korea's government has decided to raise the terrorism alert level for five diplomatic offices abroad, citing intelligence that North Korea may attempt to harm their officials.

The South Korean foreign ministry says the decision came at a government meeting on counterterrorism on Thursday.

The five offices are South Korean embassies in Cambodia, Laos and Vietnam and general consulates in the northeastern Chinese city of Shenyang and Vladivostok in Russia's Far East.

The terrorism alert level has been raised by two notches from the lowest, attention, to the second-highest, alert, that indicates there is a high possibility of a terrorist attack.

The foreign ministry says the decision is based on intelligence that Pyongyang is plotting to harm officials at those diplomatic offices.

South Korea's National Intelligence Service also said it had a number of indications that North Korea is preparing to carry out terrorist attacks against South Korean diplomatic officials and citizens.

The government said it will do all it can to ensure security, while continuing to gather information.