SEOUL, South Korea — As nerves began to calm the day after a prolonged and deadly artillery exchange between North and South Korea, focus turned on Wednesday to the possible motivations for the assault and whether the South might have provoked it.

The Koreas blame each other for instigating the artillery barrages on Tuesday afternoon. The exchange, which lasted about an hour, centered on the South Korean island of Yeonpyeong, which lies in the western sea, eight miles off the North Korean coast.

The incident killed two South Korean soldiers and President Lee Myung-bak expressed regret Wednesday afternoon over “the passing of the two marines who met a glorious death in defense of the homeland.”

The charred bodies of two civilians also were discovered as military teams canvassed the wreckage of the island. Yeonpyeong, essentially a fishing village, is about twice the size of New York’s Central Park. About 1,600 civilians live there, along with a marine garrison of about 1,000.