South Korean and US troops will carry out an anti-invasion drill on a frontline island next month in response to North Korea's construction of a hovercraft base, news reports said Saturday.

A US military spokesman said he had no information but, if confirmed, it would be the first time the two allies have conducted a joint exercise on Baengnyeong island, near the disputed sea border in the Yellow Sea.

The reports came as US Secretary of State Hillary Clinton headed to South Korea for talks with President Lee Myung-Bak.

SBS TV and Chosun daily said special troops from the two allies will conduct the drill around the middle of next month.

An unidentified military source was quoted by Chosun as saying a hovercraft base at Goampo on the North's southwestern coast was expected to be completed in June.

Goampo is some 50 kilometres (31.25 miles) north of Baengnyeong island and it would take only 30-40 minutes for a North Korean hovercraft with about 40 troops on board to reach the island, the source said.

Goampo is likely to house some 70 hovercraft, he said.

"In response to this threat, special troops of the two countries will carry out a drill on Baengnyeong island against attackers on hovercraft," the source said.

US Apache attack helicopters may take part, the daily said.

South Korea's Marine Corps said Friday it would launch a large-scale landing drill next month at Pohang, well south of the front line, in late May.

About 3,000 marines and an unidentified number of troops from the South Korean army, as well as navy ships and air force jets will be mobilised for the drill aimed to sharpen combat capabilities against North Korea.

The landing drill was originally scheduled for March, but was postponed due to a quake in Japan, the Marine Corp said.

Inter-Korean ties remain icy since South Korea blamed the North for allegedly torpedoing a South Korean warship near Baengnyeong island in March last year, in which 46 sailors lost lives.

Pyongyang angrily denied responsibility and bombarded Yeonpyeong island, also near the disputed sea border in the Yellow Sea, killing two soldiers and two civilians in November last year.