MOGADISHU - Somali security forces have rescued a South African couple kidnapped by pirates in the Indian Ocean and held for 18 months, Defense Minister Hussein Arab Isse said Thursday.

"The rescue started last night (Wednesday) and lasted until this morning and you can see that the pair were freed safely," Isse told a joint press conference with the couple, Debbie Calitz and Bruno Pelizzari.

Isse said the raid was a joint operation by security forces and the army and that the couple had been freed from "Al-Qaeda-affiliated" insurgents.

It was not immediately clear whether this meant that the pirates who captured the couple had sold them on to Somalia's Shebab rebels, a group linked to Al-Qaeda.

Sources said the operation took place in the lower Shabelle region of southern Somalia, close to Mogadishu.

Calitz and Pelizzari were sailing in the Indian Ocean off the coast of Kenya in 2010 when their yacht was hijacked by 12 pirates who set course for Somalia and took the couple ashore at Baraawe.

South Africa welcomed the news of the couple's rescue.

"The South African government wishes to express its sincere gratitude to the transitional federal government of Somalia following the release on Wednesday... of the couple," the foreign ministry said in a statement.

Pretoria said Italy was involved in the rescue operation and thanked it for its role.

"The couple is in good health and eager to be reunited with their loved ones," said the statement.

It did not give details on the rescue operation.

Asked if any ransom was paid, foreign ministry spokesman Clayson Monyela said in a text message: "It is not the policy of government to pay ransom."

Calitz, aged around 50, and Pelizzari, in his early fifties, were working as crew on the yacht Choizil as it sailed from Dar es Salaam in Tanzania toward South Africa when the hijacking occurred on October 26, 2010.

The yacht's skipper, Peter Eldridge, refused to leave with the pirates and was eventually rescued by a vessel from EU NAVFOR, the European Union's anti-piracy mission, on November 7.

Calitz's brother Dale van der Merwe said in January 2011 he had been contacted by people claiming to be the pirates who demanded a ransom of 10 million dollars (7.9 million euros).

Friends and family members of Calitz and Pelizzari set up a website to raise money to free the pair.

After the couple had spent five months in captivity the ransom demand came down to $500,000, according to the site, but after "interference with negotiations" the pirates again raised the amount to $4 million.

The Somali defence minister made no mention of any ransom payment.

He told journalists that more such raids may be staged.

"We know the whereabouts of the rest of the hostages, including the French agent, and if the kidnappers fail to free them, we will forcefully rescue them," he said, referring to a French intelligence agent seized in Mogadishu in July 2009 and detained since.