North Korea has freed three US citizens from prison, according to a tweet from US President Donald Trump.

The move is viewed as goodwill gesture ahead of a historic summit between Trump and North Korea's Kim Jong-un, reports the BBC.

Trump said he would greet the men when they return with Secretary of State Mike Pompeo, who has been in Pyongyang to arrange the planned talks.

Kim Hak-song, Tony Kim and Kim Dong-chul had been jailed for anti-state activities and placed in labour camps.

Trump announced the release of the men in a tweet on Wednesday saying, “I am pleased to inform you that Secretary of State Mike Pompeo is in the air and on his way back from North Korea with the 3 wonderful gentlemen that everyone is looking so forward to meeting. They seem to be in good health. Also, good meeting with Kim Jong Un. Date & Place set.”.

"They seem to be in good health," he wrote, adding that a date and location had been set for talks after a "good meeting with Kim Jong Un".

Trump added that he will personally greet them when they arrive at Andrews Air Force Base on Thursday.

One of the detainees was jailed in 2015, the other two have been in prison for just over a year. Their convictions have been widely condemned as political and an abuse of human rights.

The fate of the detainees has been a key factor in the build up to the Trump-Kim meeting.

Earlier this month, reports emerged that they had been moved from prison to a hotel in Pyongyang, raising speculation that they could soon be released.

South Korea's presidential Blue House welcomed the release of the Americans, saying it would have a "positive effect" for upcoming negotiations.

The last American freed by N Korea - Otto Warmbier, who was jailed for stealing a hotel sign - was released last year but was fatally ill, and died shortly after returning home. The cause of death remains unexplained.

BDST: 2005 HRS, MAY 9, 2018
AP