Myanmar’s president has declared an amnesty for 102 prisoners including Philip Blackwood, a dual British-New Zealand citizen held in the country’s most notorious jail for nearly a year.

New Zealand’s ministry of foreign affairs and trade, which handled Blackwood’s case, confirmed to the Guardian that he was on the Myanmar presidential amnesty list, which will allow him to be released from detention.

It said the embassy was “liaising with the relevant authorities over the amnesty release arrangements and will advise the family when these arrangements are determined”.

Blackwood’s mother, Angela, said on Friday the family was delighted he was included in the amnesty. “We’re a little shellshocked,” she told the Guardian, speaking from New Zealand by phone. “We hope he’ll be released either today or tomorrow or at least in the next week.”

The mass amnesty comes as Aung San Suu Kyi’s National League for Democracy prepares to sit as a majority in parliament on 1 February after it won the general election in November.

The outgoing administration of President Thein Sein, who ran a military-backed civilian government since taking over from the junta in 2011, has pushed through a series of political and economic reforms, culminating in the election that saw it voted out.

Blackwood, 33, and two Burmese colleagues were accused of insulting religion and sentenced to two and a half years in jail in March after he posted a psychedelic image of Buddha wearing headphones on the Facebook page of the bar he managed in Yangon.

It is not clear if the two colleagues will also be freed in the amnesty, under which the 102 prisoners, a number of whom were jailed for political reasons, will gradually be released.

Blackwood’s father said last year that he was being held in the infamous Insein Prison in a tiny cell with no window, an open sewer for a toilet and had lost 50lbs (20kg) since he was arrested. Aung San Suu Kyi, a Nobel peace laureate, was detained there in 2003.

A director at the president’s office, Zaw Htay, said in a statement posted on Facebook that 102 prisoners would be freed. He added that 77 people on death row would be given life in prison.

A Burmese political prisoner watchdog, the Assistance Association for Political Prisoners (AAPP), said many of the other prisoners were arrested for staging protests. In December, it said that there were 128 political prisoners in jail.

It was not immediately clear exactly how many of the 102 given amnesty on Friday were political prisoners and AAPP figures show that 403 activists are still awaiting trial for political actions.

A prison official told Reuters that 18 political prisoners had already been released from Insein Prison.

The US has slowly lifted sanctions on Myanmar as it emerges from half a century of direct military rule in which hundreds of journalists, activists and politicians languished in jail for criticism of the government.

Thein Sein, despite being a former military commander, is credited with leading the gradual handover of power to civilian authorities and has pardoned nearly 7,000 prisoners.

However, the Myanmar armed forces, or Tatmadaw, will retain significant power. Under the army-drafted constitution, the military reserves a quarter of seats in parliament and the three most powerful government ministries: home, defence and border affairs.

Reuters contributed to this report