A North Korean ship caught in July while trying to move undeclared Cuban weapons through the Panama Canal left Saturday to return to Cuba, the Foreign Ministry said.

The Chong Chon Gang freighter departed from the Panamanian port of Colon with a crew of 32, the ministry said in a statement.

The ship got the green light last week to leave Panama after Pyongyang paid a fine of nearly $700,000.

Back in July, en route from Cuba, the ship was stopped on suspicion of carrying drugs as it tried to enter the canal, the busy waterway linking the Caribbean and Pacific.

A search by Panamanian authorities uncovered 25 containers of Cuban military hardware, including two Soviet-era MiG-21 aircraft, air defense systems, missiles and command and control vehicles.

The containers were concealed under more than 200,000 sacks of sugar.

Both Havana and Pyongyang said the weapons were obsolete Cuban arms being shipped to North Korea for refurbishment under a legitimate contract and due to be returned to Cuba.

But neither country explained why the shipment was hidden if it was indeed legitimate.

The seized cargo has remained in Panama pending a court ruling on what to do with it.

The foreign ministry said that once the vessel arrives in Havana, it will be loaded with a shipment of sugar destined for North Korea.

Last month Panamanian authorities dropped charges against 32 of the 35 North Korean crew members.

The departing crew members were examined by the Red Cross and found to be in good condition, officials said.

"They've been in a perfect state and go off in good health," said Jaime Fernandez, president of the Panamanian Red Cross.

The remaining three -- the vessel's captain, first officer and political secretary -- are still in custody in Panama, facing trial on arms trafficking charges. Authorities said they face up to 12 years in prison.

During their detention at Cuba's Fort Sherman, a former US military base north of the canal, the North Koreans received regular visits from International Committee of the Red Cross, said Fernandez.

He said that during their detention the men spent time on the beach, watched television and took part in other leisure activities while awaiting permission to leave.

An attorney for the crew, said the men were nonetheless relieved to be on their way to Cuba.

The sailors "are happy because this affair in which they have lost seven months of their lives has finally come to an end," said a lawyer for the crew, Julio Berrios. He said they felt their long detention was unjust.

Panama asked the United Nations to send a mission to determine if the attempted shipment violated a UN embargo on arms deliveries to North Korea.

The results of the mission's probe have not been made public. But Panamanian authorities say the UN team's report confirms the cargo definitely violated the embargo. (AFP)