UK prime minister Boris Johnson has apologised “unreservedly” for the events involving the British army which led to the deaths of 10 people in the Ballymurphy Massacre in Northern Ireland 50 years ago.

Johnson’s spokesman said the prime minister spoke with Northern Ireland’s first minister Arlene Foster and the region’s deputy first minister Michelle O’Neill on Wednesday following Tuesday’s conclusion of lengthy inquests into the killings, which found that all the victims of the Ballymurphy shootings in 1971 were “entirely innocent”.

“The prime minister apologised unreservedly on behalf of the UK government for the events that took place in Ballymurphy and the huge anguish that the lengthy pursuit of truth has caused the families of those killed,” his spokesman said, describing the outcome of the inquest as “deeply sad”.

The inquest found that eight men and one woman, aged between 19 and 44, were killed by the British army over five separate incidents between August 9 and 11 in 1971, the early years of what would become more than 30 years of sectarian unrest in Northern Ireland before the Good Friday Agreement delivered peace in 1998.

Delivering her rulings in a series of inquests on Tuesday, the coroner, Mrs Justice Keegan, said the British army did not follow its own protocols and shot unarmed individuals who did not pose any threat, including a priest waving a white object tending to an injured man. A tenth victim, a 49-year-old man, also died but the inquest could not determine who had fired the bullet that killed him.

On Tuesday, O’Neill, the most senior Belfast politician for nationalist Sinn Féin, described the deaths as “British state murder”. Foster, the outgoing leader of the Democratic Unionist party, commended the families for their “tenacity” and said “the findings should be accepted”.

Johnson’s spokesman said the prime minister also used Wednesday’s call with the region’s leaders to restate “the government’s intention to deliver a way forward in Northern Ireland that focuses on reconciliation, delivers for victims of the Troubles and ends the cycle of reinvestigations”.

In Tuesday’s Queen’s Speech, the UK government set out plans to introduce “legislation to address the legacy of the Troubles in Northern Ireland”. But it has not yet confirmed leaked plans for a controversial amnesty on crimes committed during that period.

Foster said the prime minister also briefed her and O’Neill on the UK government’s approach to the Northern Ireland protocol governing post-Brexit trade in the region, which Lord David Frost, the UK’s minister responsible for EU-UK trade relations, on Tuesday warned would not be “sustainable for long”.

“It is clear the protocol needs to be replaced to restore the free flow of goods from GB-NI,” Foster said, articulating ’ long-held unionist opposition to measures that impose a trade barrier between Northern Ireland and Great Britain in order to avoid any barrier on the island of Ireland. The DUP is party to a legal challenge to the protocol but Northern Ireland does not have any formal role in talks between the UK and EU.