Rival political parties here urged North Korea Wednesday to apologize and take responsibility for the deadly sinking of a South Korean warship four years ago.

The ruling Saenuri and main opposition Democratic parties made the calls as South Korea mourned the deaths of 46 sailors in the sinking of the Cheonan near the western sea border with North Korea exactly four years ago.

A joint international investigation into the sinking concluded that North Korea torpedoed the ship, but Pyongyang has flatly rejected the accusation, claiming the investigation results were fabricated.

Some South Koreans, especially from the liberal opposition bloc, have also questioned the veracity of the probe results. On Wednesday, however, both the ruling and opposition parties denounced North Korea for the sinking.

"We urge North Korea to stop armed provocations that threaten security on the Korean Peninsula and inter-Korean relations, and (demand Pyongyang) offer a sincere apology and take sincere steps to prevent a recurrence (of such incidents)," ruling party spokeswoman Min Hyun-joo said in a statement.

The opposition party also urged the North to apologize for the sinking and adopt a forward-looking approach.

"There is nothing to gain from escalating tensions on the Korean Peninsula through armed provocations," opposition party spokeswoman Han Jeoung-ae said in a statement.

The ruling party's floor leader Choi Kyoung-hwan questioned the opposition party's sincerity in attending a memorial service for the victims en masse.

"It looks like they were desperate for votes ahead of the elections," he said in a phone interview with Yonhap News Agency, referring to the upcoming local elections in June.

"They should first clearly indicate their stance on whether North Korea is responsible for the sinking of the Cheonan." (Yonhap)