Seoul, June 1 (IANS): Barely weeks after North Korea announced its first launch of a ballistic missile from a submarine, South Korea and the US conducted their biggest joint anti-submarine naval exercise, the Seoul government announced on Monday.

The five-day military drill on South Korean waters close to Jeju island began on Saturday with the aim of "deterring submarine-related provocations", a South Korean defence ministry spokesperson told Efe news agency in a clear reference to North Korea.

Although the drill is one of the frequent ones, Seoul has confirmed that it is the largest conducted by the two allied forces ever.

In the manoeuvres -- ending Wednesday -- more than 10 ships, two submarines and a P-8 US surveillance aircraft equipped with air-to-surface missiles participated, the spokesperson confirmed.

The drill comes three weeks after May 9 when the regime of Kim Jong-un announced in its state-run media the “successful” launch of a ballistic missile from a submarine called SLBM.

South Korea and the US have shown concern over the action because if North Korea deployed such types of missiles, it could pose a potential threat to both countries.

These projectiles are difficult to intercept and could carry nuclear warheads.

Experts, however, have doubted the truth behind the SLBM launch, since this requires very advanced techniques and raised the possibility of the images being doctored or the ejection being conducted from an underwater platform.

Seoul and Washington, nevertheless, have taken the threat seriously and announced that they would take measures.

South Korea has asked the UN Security Council to intervene in the matter.

The UN previously imposed sanctions on North Korea over nuclear and missile tests, and several of its resolutions explicitly prohibit Kim's regime from making ballistic missile launches.