Seoul's defence minister on Sunday vowed retaliation over the sinking of a South Korean warship which killed 46 sailors near the disputed sea border with North Korea last month.
"Those responsible for killing our soldiers must pay the price," Defence Minister Kim Tae-Young told a KBS television programme aired nationwide on Sunday.
"Retaliation -- in whatever form it is -- must be done."
It echoed South Korean Navy chief Admiral Kim Sung-Chan's reprisal pledge during Thursday's mass funeral for the sailors, attended by President Lee Myung-Bak.
South Korea has not openly blamed its communist neighbour for the blast which tore apart the 1,200-tonne corvette Cheonan in the Yellow Sea on March 26.
But tensions between Pyongyang and Seoul have been simmering since the sinking, with suspicions growing that the North might have been behind the incident. The North denies involvement.
Defence Minister Kim told the KBS show on Sunday that tiny "slivers of aluminium" collected from where the ship went down were being examined to see if they came from weapons used to sink the ship.
Kim has said a heavy torpedo was among the likeliest causes of the sinking. However, he cautioned that the aluminium pieces, three millimetres (0.12 inches) in size, were not yet treated as "decisive" evidence, adding the probe should clarify if they belong to the vessel or something else.
Searchers are scouring the seabed for any other clues that could confirm whether the Cheonan was attacked.
The area was the scene of deadly naval clashes in 1999 and 2002, and of a firefight last November which set a North Korean patrol boat ablaze.
The sinking of the warship has effectively put a brake on diplomatic efforts aimed at reviving six-nation nuclear disarmament talks on North Korea.
The North has also seized some assets owned by Seoul at the North's Mount Kumgang tourist resort and announced it would let a new partner take over the tour business there from South Korea's Hyundai Asan.