South Korea on Thursday will present clear and definitive material evidence related to the mysterious sinking of its warship in March, President Lee Myung-bak said Wednesday.

The bow of the sunken South Korean naval vessel Cheonan is lifted by a giant crane off Baekryeongdo island, near the maritime border with North Korea, northwest of Seoul, South Korea, April 24, 2010. [Newsis/Xinhua]

Lee made the remark during a 20-minute phone call with Japanese Prime Minister Yukio Hatoyama late Wednesday, according to a press release from Cheong Wa Dae, the presidential office of South Korea.

South Korea will present evidence that can't be refuted by any country or person while announcing the outcome of an investigation conducted by a multinational team on the cause of the sinking of its Cheonan frigate, Lee was quoted as saying.

In the phone conversation, Lee and Hatoyama agreed on close cooperation and pushing for strong international collaboration in taking follow-up measures after the announcement, the press release said.

The press release did not mention whether Lee directly touched upon who is responsible for the incident.

Foreign Minister Yu Myung-hwan told local reporters earlier that the involvement of the Democratic People's Republic of Korea (DPRK) in the Cheonan incident was "obvious," saying that the ongoing investigation has revealed that the previously unidentified explosion was caused by "the detonation of a torpedo."

The DPRK has denied involvement in the sinking of the Cheonan.

The Cheonan, which carried 104 crew members, sank on March 26 in waters off the west coast of the Korean peninsula, which was the scene of two deadly naval skirmishes over the past decade. The warship sank after an unexplained blast split the ship in half. Fourty-six sailors were killed.

The South Korean government formed a joint probe involving civilian, military and foreign experts, and the results were expected to be released on Thursday.