Pyongyang fired four short-range unidentified projectiles into the sea off its east coast on Monday, reported South Korean military officials.

The projectiles, which were either rockets or missiles, launched from the southern city of Hamhung and traveled 200 km (120 miles) before landing in waters to the east of North Korea, said South Korea's Joint Chiefs of Staff in a statement.

Monday's short-range tests come just three days after the North fired two medium-range ballistic missiles into the sea in defiance of strict new UN and US sanctions which were slapped on the country earlier this year.

The UN Security Council condemned last Friday's launches as "unacceptable" and said they were a clear violation of existing UN resolutions.

The North's latest launches appear to be the isolated communist regime's response to the annual springtime US-South Korean military drills. The North maintains that the maneuvers, which are the largest they have ever been, are an invasion rehearsal.

Last week, North Korean leader Kim Jong-Un said his country soon intends to test a nuclear warhead and ballistic missiles - a move which is in direct violation of the UN Security Council's latest resolutions which are backed by the North's ally China.

Tensions on the Korean peninsula have been at an all-time high since the North conducted its fourth nuclear test on January 6, followed by a long-range rocket launch which was believed to be a ballistic missile test.