JOINT BASE LEWIS-MCCHORD, United States (AFP) - The last two Americans serving lengthy prison sentences in North Korea arrived home on Saturday after the reclusive state freed them following a secret mission by United States intelligence chief James Clapper.

Mr Kenneth Bae and Mr Matthew Miller arrived around 9pm at Joint Base Lewis-McChord in Washington State. The men disembarked the US government plane with luggage, then embraced family and friends on the tarmac.

They arrived with heads shaved. Mr Bae wore khakis and a dark shirt, while Mr Miller wore dark pants, a jacket and grey shirt.

North Korea's surprise release of Mr Bae and Mr Miller followed the equally unexpected decision by Pyongyang last month to free 56-year-old US national Jeffrey Fowle. Earlier in the day, President Barack Obama hailed the latest releases as "wonderful," as State Department officials said there had been no "quid pro quo" deal with North Korea to secure Mr Bae and Mr Miller's freedom.

"The Department of State welcomes the release of US citizens Kenneth Bae and Matthew Todd Miller from the DPRK, where they have been held for two years and seven months, respectively," a statement said, using the official acronym by which the North is known.

US Director of National Intelligence Clapper traveled to North Korea and "engaged on behalf of the United States in discussions with DPRK authorities about the release of two citizens", the statement said.

A senior administration official said Mr Clapper carried a "brief message" from Mr Obama to North Korean Leader Kim Jong Un, indicating he was his personal envoy to bring the Americans home.

"It was a skillful move on the part of the administration," former US envoy to the United Nations Bill Richardson, who engaged in negotiations with the North in the past, told CNN about the note from Mr Obama.

Mr Obama, speaking just hours before leaving for a swing through Asia, praised Mr Clapper's role in the "challenging" mission.

"I think it is a wonderful day for them and their families and obviously we are very grateful for their safe return," he said.

Former basketball great Dennis Rodman, who has talked up his cozy relationship with Mr Kim, claimed his trips to the country had triggered Mr Bae's release.

"I understand the crimes (Mr Bae) committed, and ask you my dear friend, the highly respected Marshall Kim Jong Un for his release to show my country how loving and compassionate you and the DPRK can be," Rodman wrote in a letter to the leader in January released by celebrity website TMZ.

Mr Bae, a Korean-American missionary, earlier this week marked the two-year anniversary of his detention.

The sickly 46-year-old was arrested in November 2012 and later sentenced to 15 years' hard labour.

Mr Bae's sister Terri Chung expressed joy at her brother's release.

"We have been waiting for and praying for this day for two years. This ordeal has been excruciating for the family, but we are filled with joy right now," she said in a statement.

"He will not have to spend another day at a labor camp. He can now recover from this imprisonment and look forward to his wife, kids and rest of his life.

"Our Thanksgiving celebration this year will be one we will never forget."

Mr Bae was born in South Korea and his family immigrated to the United States in 1985, his sister said.

Mr Miller, 24, had been sentenced to six years' hard labor by the North Korean Supreme Court following his arrest in April, after he allegedly ripped up his visa at immigration and demanded asylum.

Washington had condemned Pyongyang over the detentions, saying the Americans were held as political hostages to extract diplomatic concessions.

North Korea has expressed interest in the past in reviving six-party talks with the US and others about its nuclear program, but Washington insists Pyongyang must first show a tangible commitment to denuclearization.

A State Department official insisted the release of Mr Bae and Mr Miller did not reflect a shift in posture over the mothballed nuclear negotiations.

"North Korea knows what it needs to do if it wants a better relationship with the international community and wants to end its isolation and pariah status," the official told AFP.

"North Korea must show it is serious and prepared to abide by its commitments, particularly concerning denuclearisation. And they must take significant steps to improve their human rights record.

"The release of our citizens is unrelated."

As recently as Tuesday, North Korea was maintaining its defiant stance, ruling out dialogue with the United States about its nuclear programme and human rights record and accusing the US of trying to destroy its system.

The North "will never allow any human rights dialogue or nuclear one with the enemy keen to overthrow it", a Foreign Ministry spokesman said through the official Korean Central News Agency.