As the pace of the 'Burmese Spring' accelerates, release of political prisoners will be crucial to lifting EU and US sanctions

There is no "concrete" reason why hundreds of Burma's political prisoners could not be released without delay, according to a spokesman for the country's authoritarian regime.

The pace of the Burmese "spring" appeared to accelerate this weekend as the regime revealed plans to make peace with ethnic rebels, release more prisoners and ease state censorship.

It came as Hillary Clinton arrived in the country for a two-day visit, the first by a US secretary of state in more than 50 years. Praising reforms made since the March elections when the military gave way to a civilian one, albeit in a parliament stacked with former generals, she urged more.

The UK's development secretary, Andrew Mitchell, visited last week and on Saturday the UN discussed strengthening co-operation with the reclusive state as UN secretary general Ban Ki-moon said he had accepted an invitation from President Thein Sein to visit Burma "as soon as possible".

The president's chief adviser, Ko Ko Hlaing, admitted to reporters that there was an internal debate in the government over the pace of change, with some wishing to keep it slow, but added: "I can't say exactly the time but there is no concrete reason to delay the release of the political prisoners."

He said, too, that the government wanted to see the 230 activists freed in an amnesty in October integrated into the political process. "As you can see in the Arab states and also in Syria, there is some turmoil. Even in Egypt, there were mobs. So what our leaders would like to see is a stable and smooth transition to democracy," he said.

"We don't know all about the democratic systems but we are trying our best to make an effective transition to democracy. We have to change mindsets and the attitude of all society. It is very difficult to change a mindset," he said.

Meanwhile on Friday, Burmese opposition leader and Nobel Peace prize winner Aung San Suu Kyi officially re-entered electoral politics when her pro-democracy National League for Democracy (NLD) party registered to contest forthcoming by-elections. It will be the first time in her political career that she has competed for a parliamentary seat after the party boycotted previous elections and was subsequently declared illegal. Aung San Suu Kyi was held under house arrest for most of the past two decades, before her release in November last year.

"Our party will be registered and we will compete in the elections," party chairman U Tin Oo told the Observer. He said the decision had been reached after examining reforms to electoral legislation made earlier this year.

Aung San Suu Kyi, who was awareded the Wallenberg medal for humanitarian action this year, says about 400 NLD activists remain in jail. Freeing political prisoners is crucial to lifting EU and US sanctions that have isolated Burma and pushed it closer to China.

The regime has has also promised new media lawsafter years in which every song, book and painting had to pass the censors. "Our new media law will reflect guaranteed freedom of expression, so no censorship. But there will be some monitoring systems," said Ko Ko Hlaing. "The censorship will only be cultural and religious. Other than that, they can express opinions freely."