SEOUL, South Korea — Evidence overwhelmingly proves North Korea fired a torpedo that sank a South Korean warship in March, killing 46 sailors, investigators said Thursday.

South Korean President Lee Myung-bak vowed “stern action” for the provocation and called an emergency security meeting for Friday, the presidential Blue House said.

“(We) will take resolute countermeasures against North Korea and make it admit its wrongdoings through strong international cooperation,” Lee told Australian Prime Minister Kevin Rudd in a phone call, the presidential office said.

The long-awaited investigation results from a multinational team said a torpedo caused a massive underwater explosion that tore the Cheonan apart on March 26.

Fifty-eight sailors were rescued from the frigid Yellow Sea waters near the Koreas’ maritime border but 46 perished.