Naypyidaw: Myanmar said on Saturday it freed more than 300 political prisoners in its most significant amnesty yet, a move which prompted the United States to pledge it would restore full diplomatic ties.

Friday’s releases, which included a number of prominent dissidents, were hailed by Western powers that have long demanded the freeing of political detainees before they will consider lifting sanctions on the isolated nation.

US President Barack Obama said the amnesty was a "substantial step" towards democracy in a country ruled for decades by the military, while the party led by democracy champion Aung San Suu Kyi called it a "positive sign".

Myanmar said yesterday about 650 inmates were included in the mass pardon, but it had not been clear how many were political prisoners.

Home Affairs Minister Lieutenant General Ko Ko said that 302 of those released were on a list of political detainees compiled by a political group, thought to be Suu Kyi's opposition National League for Democracy (NLD) party.

He insisted that none of those had been jailed for political reasons.

"We didn't take action against anyone because of politics or beliefs," he told reporters.

"This release was not according to the demand of any person or any organisation. We released them according to the true benevolence of the government."

It is not clear how many more political prisoners are still behind bars, but Ko Ko said 128 people remained on the list submitted by the unnamed political group.