South Korea and the United States launched a new round of war games on Monday involving tens of thousands of troops, despite threats of retaliation from North Korea.

The 10-day computerised military exercise is one of a series being staged by by the South — either alone or jointly with the United States — in the aftermath of the sinking of one of its warships in March.

Pyongyang warned on Sunday that its army and people would “deal a merciless counterblow” to the United States and South Korea over the war games.

The massive military drill involving some 30,000 US troops and 56,000 South Korean troops began on Monday, a spokesman for South Korea’s defence ministry said.

The sinking of the corvette the Cheonan in March with the loss of 46 lives sharply raised tensions on the Korean peninsula, with a multinational inquiry determining that it was caused by a North Korean torpedo.

Pyongyang has vehemently denied it was involved in the sinking and threatened retaliation for this week’s military exercises, which it branded preparations for a full-scale “military invasion.”

In a message posted on a US military website, General Walter Sharp, who heads some 28,500 US troops based in the South, described the exercise as “one of the largest joint staff directed theatre exercises in the world.”