South Korea's military said it was holding live-fire drills on Tuesday off its country's east coast involving anti-ship missiles and jet fighters after North Korea conducted a submarine-launched ballistic missile test condemned by Seoul and Washington.

The joint naval and air force exercise involves some 20 warships as well as an unspecified number of jet fighters, Seoul's defence ministry deputy spokesman Na Seung-Yong told reporters.

"The ongoing live-fire drills involving anti-ship guided missiles and other strategic training for navy and air force troops...are aimed at quashing the North's intention for provocations at sea," Na said.

The exercise came as military tension rose on the Korean peninsula following the North's launch of the SLBM, a weapon feared to take the country's nuclear threat to a new level.

The North's state media announced on May 8 that the new SLBM had been tested under the personal supervision of leader Kim Jong-Un.

The test, if confirmed, is a violation of a United Nations ban on the North's use or testing of ballistic missile technology, imposed after a series of missile and nuclear tests.

Tension further escalated after Pyongyang followed up the SLBM launch by test-firing three anti-ship cruise missiles and held a live-fire drill near the disputed sea border off its west coast.

Seoul condemned the SLBM test as "worrisome" and US Secretary of State John Kerry warned on Monday of the possibility of imposing fresh sanctions on the isolated state.

A fully-developed SLBM capability would allow the nuclear-armed North to deploy weapons far beyond the Korean peninsula.

The South Korean military estimated last week that it could take up to five years before Pyongyang is able to deploy a fully operational submarine armed with ballistic missiles.