By Shaun Tandon

DULLES INTERNATIONAL AIRPORT, Virginia: A US activist freed by Myanmar returned home Friday to be reunited with his fiancee but said he would only be happy if the regime releases thousands more prisoners.

Kyaw Zaw Lwin, 40, a Myanmar-born rights activist who holds US citizenship, recounted what he called "mental torture" in the six months since his arrest, during which he said he was kept mostly in a solitary, insect-infested cell.

A small crowd of fellow Washington area residents originally from Myanmar, earlier known as Burma, cheered him and offered congratulatory balloons as he walked off his commercial flight with a State Department escort.

Kyaw Zaw Lwin, who was thin and suffers leg pains but spoke lucidly, immediately embraced his fiancee Wa Wa Kyaw, a nurse also born in Myanmar who had lobbied the US government to take up his case.

"I am really happy to meet my fiancee... but my family and all my friends stay in prison, so I feel not really happy," said Kyaw Zaw Lwin, who also goes by the name Nyi Nyi Aung.

"I learned from people how much they really want to get freedom," he said. "They are really trying hard, but the regime is so terrible.

"I have a lot of responsibility to do more for a free Burma," he added.

Kyaw Zaw Lwin said he traveled to Myanmar to visit his mother, who is herself detained for political activities and is suffering from cancer. He never saw her.

He was arrested on September 3 and said he was deprived of food and water during his first two weeks of detention. The treatment later improved, but only slightly.

"The prison is physically fine, but mentally they torture," he said, recalling he stayed in a dark room with a vile stench.

"There were a lot of insects. In the nighttime you couldn't sleep -- the dog is barking. All day long you have to stay in that cell."

Kyaw Zaw Lwin said he would seek medical assessment on his leg, which gives him pain after the solitary confinement.

He was sentenced to three years in prison in February on charges of forging an identity card, failing to declare currency at customs and violating immigration law for not formally renouncing his earlier nationality.

After his sentence, his supporters were critical of US President Barack Obama's administration, saying it failed to take up Kyaw Zaw Lwin's case as they pursue a new policy of dialogue with the junta aimed at ending its isolation.

His fiancee Wa Wa Kyaw wrote an opinion piece in The Wall Street Journal Asia, saying she felt "betrayed" by her adopted country for not doing enough in this human rights case.

The couple went out of their way Friday to thank the administration.

Wa Wa Kyaw said she was "very happy" with the State Department and that she had been in contact with Kurt Campbell and Scot Marciel, top US officials handling Asian affairs.

The regime released Kyaw Zaw Lwin as it comes under intensifying international criticism ahead of elections it plans later this year.

The United States has warned that the election will be a "mockery" of democracy as the regime plans to disqualify pro-democracy forces. Rights groups say the regime holds more than 2,000 political prisoners.

Myanmar's last elections in 1990 were swept by democracy icon Aung San Suu Kyi's National League for Democracy. But the junta never allowed her to take over and has kept her under house arrest for most of the time since.

Kyaw Zaw Lwin said he was given no reason for his release and that only Myanmar's leader, Senior General Than Shwe, knew for sure.

"He doesn't understand what he's doing," he said.

"If he understood the message of the people of Burma and the message from the international community, Burma would change because it's easy to have a dialogue with Aung San Suu Kyi and other democratic leaders."

Kyaw Zaw Lwin said he had not yet decided how active to be in the democracy movement -- but had no plans to return to Myanmar anytime soon.

Tin Thu, a physician and family friend who came to welcome him, said she was surprised Kyaw Zaw Lwin took the risk of returning to their native country.

"We didn't even know he had gone back," she said. "Once we knew, all of us were scared."