Ethiopia on Monday pardoned and freed two Swedish journalists who were arrested last year in the rebel Ogaden region and had been serving an 11-year jail sentence for "supporting terrorism".

The pardon was approved by the late prime minister Meles Zenawi before his death last month and comes days after Sweden's foreign minister attended his funeral in Addis Ababa.

"Yes they are already released," foreign ministry spokesman Dina Mufti told AFP of reporter Martin Schibbye and photographer Johan Persson.

He said the pair, who have been held in an Ethiopian jail since their arrest on July 1, 2011, were freed Monday but he was unable to elaborate on their whereabouts.

Justice Minister Berhan Hailu said the two journalists were expected to fly out of Ethiopia within a day.

"The decision was made on the 12th of July," when Meles was still alive, he told reporters. "According to the constitution, they have to leave the country within 24 hours."

An official had said earlier that the pair were to be released as part of a mass pardon traditionally granted by the president to coincide with the Ethiopian New Year.

"The prime minister approved the liberation of the two Swedish journalists before he went into hospital," the official had said on condition of anonymity.

Schibbye and Persson were arrested with rebels from the Ogaden National Liberation Front (ONLF) after illegally entering from Somalia and were sentenced in December to 11 years in prison for "supporting terrorism".

Swedish Foreign Affairs Minister Carl Bildt was one of the few Western ministers who attended the funeral in Addis Ababa of Prime Minister Meles Zenawi on September 2.

His presence at the funeral fuelled speculation that the Ethiopian authorities, under intense international pressure over the detention of the Swedish journalists, could take advantage of the New Year pardons to free them.

Schibbye's mother expressed her relief at the news of her son's release.

"Right now I'm just very, very happy, and oh how we've waited for this day," Karin Schibbye told Swedish news agency TT.

There was no immediate reaction from the government but the Swedish Union of Journalists hailed the decision to release the pair.

"I am so very glad that Martin (Schibbye) and Johan (Persson) have been freed after 14 months in an Ethiopian prison. I hope they can be reunited with their families as soon as possible," union chief Jonas Nordling said in a statement.

"We hope they will be home on Swedish ground soon," Lotta Schuellerqvist, of the Swedish branch of French-based watchdog Reporters Without Borders, said in the same statement.

The case had drawn heavy criticism from rights groups. The journalists were convicted under Ethiopia's anti-terror law, which critics have called vague and indiscriminate.

The freelance journalists were in the remote southeastern region of Ogaden, populated mainly by ethnic Somalis, to investigate the activities of a company affiliated with the Swedish oil firm Lundin Petroleum.

Press watchdog Committee to Protect Journalists has said Ethiopia has one of the most restricted media in the world, with 79 journalists forced into exile since 2001.

It was not immediately clear whether Ethiopian journalists who were also detained under the anti-terror law would be released as part of the wave of presidential pardons, which officials expect to affect around 2,000 people.

"Despite this development, other journalists remain in prison and we hope that Ethiopia will release them as soon as possible," IPI Deputy Director Anthony Mills said in a statement.