SEOUL, South Korea — The scent of incense filled the air today as South Korea's president bowed before a memorial for young sailors killed when their warship sank in an explosion the defense minister says was most likely caused by a torpedo.

A solemn President Lee Myung-bak joined mourners in paying his respects to the 46 men who went down with the Cheonan on March 26 after an explosion ripped the ship in two. He laid a single white chrysanthemum at an altar set up for five days of mourning.

"The Republic of Korea will never forget your honorable sacrifice," Lee wrote in a condolence book.

The government has not blamed North Korea outright for the disaster, one of South Korea's worst, but suspicion has focused on the regime, given its history of provocation and attacks on wartime rival South Korea.

Pyongyang has denied involvement.