Burmese authorities have freed more than 450 detainees in a goodwill gesture before a historic visit by the US president, Barack Obama. But human rights campaigners said the list of released prisoners did not include any political dissidents.

Announcing the amnesty – the latest in a series that have coincided with high-profile visits of foreign dignitaries or trips by senior Burmese leaders overseas – state media said late on Wednesday that its aim was "to help promote goodwill and the bilateral relationship".

A home ministry official told Reuters that an unspecified number of the country's remaining 300 or more political detainees would be released.