Seoul said Wednesday its military would launch major live-fire drills this week to mark the first anniversary of the sinking of a South Korean warship near its border with the North.

South Korean jet fighters and artillery units will stage a joint exercise on Thursday near the tense land border with North Korea, the defence ministry said.

The exercise at Pocheon, 30 kilometres (20 miles) north of Seoul, will be followed by massive naval firing training on Saturday, it said.

The South started a week-long sea exercise from Monday in a show of strength marking the first anniversary of its warship sinking on March 26 last year near the disputed Yellow Sea border, a ministry spokesman said.

The South accused the North of torpedoing the ship with the loss of 46 lives. Pyongyang denies the charge.

Newspapers said South Korean warships and aircraft would be mobilised for three-day training from Friday to simulate attacks by North Korean submarines, ships and jet fighters.

The state-run Korea Hydrographic and Oceangraphic Administration has issued a warning for civilian ships that naval firing drills will be held on Saturday at three locations off the peninsula.

It also warned of more offshore firing drills any time between March 28 and April 1.

The South, which has remained technically at war with its nuclear-armed neighbour since their conflict 60 years ago, says its drills are defensive.

But tensions between the two nations have risen since the North shelled a border island on November 23, killing four people.

US and South Korean troops launched their annual Key Resolve/Foal Eagle drills on February 28. They completed computerised war games on March 10, but joint field training will continue throughout March and April.

The two exercises, denounced by North Korea as a rehearsal for invasion, involve a total of 12,300 US troops and some 200,000 South Korean service members including reservists.

From Tuesday, the allies have been staging a three-day sea exercise to improve their ability to move large amounts of military equipment and supplies without a fixed port.

Twenty-four ships and amphibious vehicles are taking part in the drill, the first of its kind in the Yellow Sea, the defence ministry said.

South Korean officials and civilian groups are holding various memorial events this week.

A group of North Korean defectors will launch propaganda leaflets on Friday or Saturday from a frontier island, despite Pyongyang's threats to open fire with artillery in retaliation for pamphlet distribution.

They plan to fly some 200,000 leaflets containing news of Arab uprisings and calling for the overthrow of the North's regime.

The South's military has also reportedly sent leaflets with news of the Middle East revolts.