|Funerals for those killed in Yeonpyeong were held on Monday as Seoul launched the navy drills [Reuters]
The International Criminal Court (ICC) is looking into whether North Korea's recent shelling of a South Korean island and the sinking of a warship could constitute war crimes.
The court's prosecutor announced the investigation in The Hague on Monday, as South Korea began nationwide live-fire naval exercises, despite warnings from Pyongyang that the drills are "provocative".
Tensions on the Korean peninsula have been mounting since the two countries exchanged artillery fire on November 23. Artillery shells from the North hit Yeonpyeong Island, close to a disputed maritime border in the Yellow Sea killing at least four people.
"Luis Moreno-Ocampo confirmed that [his office] has opened a preliminary examination to evaluate if some incidents constitute war crimes under the jurisdiction of the court," a statement from the prosecutor’s office said.
On March 26, a torpedo allegedly fired from a North Korean submarine sunk the Cheonan, a South Korean warship, killing 46 sailors.
'Hell-bent on war'
North Korea, which has denied sinking the Cheonan, has said that the latest military exercises, expected to last for a week, showed that the South was "hell-bent" on setting off a war.
The exercises are scheduled to take place at 29 sites in seas near the disputed Northern Limit Line (NLL).
Al Jazeera's Marga Ortigas, reporting from Seoul, said the timing of the naval drills seemed "rather inappropriate considering the way things have been here over the last two weeks".
She said it is part of the South Korean government's efforts to "take more forceful steps when it comes to dealing with North Korean provocation".
"The previous defence minister was let go for failing to protect the country," she said.
"But now South Korea has a new defence minister who is determined to show he is a man of his word. There are many expectations resting on his shoulders."
North Korea disputes the NLL, a sea border established by the United Nations, without Pyongyang's agreement, at the end of the 1950-53 Korean War.
The locations of the drills include the Daecheong Island, one of five major islands near the Yellow Sea border, where the Cheonan, a 1,200-tonne South Korean naval vessel, was hit by a suspected North Korean torpedo in March. An international investigation blamed North Korea for the sinking.
But military officials have previously said the drills would not take place near Yeonpyeong.
The live-fire exercise came as Japan and the US stage one of their biggest-ever joint military exercises, which began on Friday, just days after the United States and South Korea conducted smaller exercises aimed at deterring an aggressive North Korea.