Beflast: Police in Belfast have arrested a man in connection with the murder of a former city commander of the hardline anti-peace process paramilitary group, the Continuity IRA (CIRA).

Tommy Crossan, 43, was shot dead at a west Belfast fuel depot in an execution-style killing shortly before 5pm on Friday.

The Police Service of Northern Ireland (PSNI) said the man, 26, was arrested on Saturday morning in west Belfast by officers from its serious crime branch and is being questioned at a police station in Antrim.

Crossan, an ex CIRA prisoner who led a hunger strike in Maghaberry prison 14 years ago, had been expelled from CIRA a few years ago during an internal power struggle. Earlier this year the PSNI informed him there was a threat to his life.

Northern Ireland’s first minister, Peter Robinson, and his deputy, Martin McGuinness, both condemned the killing.

Robinson said: “The small minority of people who want to continue terrorising the community need to understand that they will not be allowed to drag Northern Ireland back to the dark days of the past. They must be hunted down and brought to justice.”

McGuinness added: “The people behind this killing are criminals and will further no cause through this shooting. Whoever carried out this act has nothing to offer the community and have no role to play in our future.”

Last week a former CIRA killer, Declan “Fat Deccy” Smith, was buried in his native Belfast after being assassinated outside a Dublin creche at the end of March.

Smith had been blamed for the double killing of two rival republican dissidents, Eddie Burns and Joseph Jones, who were murdered in 2007 in Belfast. Jones had been tortured and beaten to death with a spade over a dispute about the seizure of weapons and the control over the republican faction.

In a statement from the Continuity IRA’s leadership on Friday, the terror group singled out a number of former members whom they accused of “criminal activity perpetrated in the name of the republican movement”.

Referring to an attempted coup four years ago against the CIRA command, the organisation said: “The treachery of 2010 was a carefully planned attempt to arrest and destroy the republican movement as it exists today in the continuing defence of the Irish Republic proclaimed at the GPO Dublin in 1916. These people have failed and the criminal conspirators they have left in their wake shall dissipate.”

And in a warning to its rivals, the paramilitary organisation added: “There will be other attempts to raise issues of contention ranging across diverse matters, for example principles, structures, authority, democracy, discipline and many others into the future. That said nobody is going to put the republican movement in their pocket and walk away to self-serve, for in doing so they will be turning away from the principles which sustain this movement and which are the ultimate guarantee of our success.”

Crossan led a prison protest for political status in Maghaberry and at one stage spent 23 hours a day locked in his cell as punishment for refusing to do prison work.

In an interview inside Maghaberry jail outside Belfast, Crossan was defiant about “armed struggle” continuing despite rising support for Sinn Fein and the peace process.

He said: “I am confident that the armed struggle will go on outside here and that, sadly, will mean more of my comrades being jailed and sent into this place. The bigger we get, the harder it will be for the authorities to treat us as criminals.”

The CIRA was formed after splits in Republican Sinn Fin (RSF) in 1986. However, it was mainstream Sinn Fin’s decision to sign up to non-violence principles during all-party talks in the run up to the 1998 Good Friday Agreement that finally prompted Crossan to leave the Provisional IRA.

The Northern Ireland secretary, Theresa Villiers, also condemned “this brutal murder which has left a family bereaved”.

Jennifer McCann, Sinn Fin assembly member for West Belfast, said that killing took place in a very busy part of the Springfield Road.

“Those behind it had no consideration for anyone in this community except themselves and their own criminal agenda.

“They have shot a man dead and endangered anyone in the immediate vicinity. There is now a family in mourning and a community traumatised by this shooting.”

The CIRA is the most hardline of the armed groups opposed to the Northern Ireland peace process. It was responsible for the 2009 murder of Constable Stephen Carroll in Craigavon. He was the first officer of the Police Service of Northern Ireland to be killed by republican paramilitaries.

Members of the security forces have been on high alert for attacks by various extremist factions who have also killed two soldiers and a prison officer.

In recent weeks they have stepped up efforts to kill police officers, with several attacks on the force in west Belfast.