U.S. helicopters swooped into central Somalia on Wednesday and rescued two hostages, an American and a Dane, from pirates in a rare raid into the Horn of Africa nation to free foreign captives.

American Jessica Buchanan and Dane Poul Hagen Thisted were working for the Danish Demining Group (DDG) when they were kidnapped from the town of Galkayo in the semi-autonomous Galmudug region in October.

"The Danish Refugee Council hereby confirms that Jessica Buchanan and Poul Hagen Thisted have been rescued earlier today during an operation in Somalia," the aid group said in a statement.

"The two aid workers from the Danish Refugee Council's demining unit, DDG, are both unharmed and at a safe location," it said.

Galmudug's president, Mohamed Ahmed Alim, told Reuters nine pirates were killed and five captured during the resuce operation near the pirate haven of Haradheere.

Alim was speaking from Hobyo, another major pirate base north of Haradheere, where he said he was negotiating to secure the release of an American journalist kidnapped on Saturday.

"About 12 U.S. helicopters are now at Galkayo. We thank the U.S. Pirates have spoilt the whole region's peace and ethics. They are mafia," Alim said.

While U.S. and French forces have intervened to rescue pirate hostages at sea before now, attacks on pirate bases are very rare. The only U.S. base in sub-Saharan Africa is in neighbouring Djibouti.

NBC News, citing U.S. officials, reported that two teams of U.S. Navy SEALs landed by helicopter and rescued the hostages after a gun battle with the kidnappers. The freed hostages were taken by helicopter to an undisclosed location, NBC reported.

President Barack Obama was overheard congratulating Defense Secretary Leon Panetta, apparently for the success of the rescue operation, as Obama entered the House of Representatives chamber on Tuesday night to give his annual State of the Union speech.

"Leon. Good job tonight. Good job tonight," Obama said. He did not mention the rescue during his speech.