Mackin comes from a well-known republican family, and Harte has been described as a senior Belfast republican activist.
The find consisted of six handguns, an assault rifle, a number of timing devices and a 10,000 rounds of ammunition in a warehouse. The Police Service of Northern Ireland said that the weapons and timers were ready for use. It is believed that they originated in Croatia.
The discovery has sparked anger among Unionists. Ulster Unionist Party leader David Trimble said on Monday that it was “potentially a very significant development.” He demanded answers from Sinn Fein.
“What is going on?” Trimble asked. “What are you up to? You tell us you want to pursue peace and politics so why is this happening?”
Speaking in Dublin, Britain’s Northern Ireland secretary, Paul Murphy, said he wanted to see the police reports on the seizure.Irish Foreign Affairs Minister Brian Cowen said: “These matters are serious in themselves, but we await the police report.”
The Sinn Fein president, Gerry Adams, was dismissive of the controversial find. People should “not get into a tizzy” over the find, he said, adding that the real challenge was to get the peace process back on the rails.
“There are obviously arms dumps out there. That the arms aren’t being used I think is a significant factor,” Adams said.
Responding to questions on sanctions against Sinn Fein for IRA actions, Adams said: “We have no problems with structures to ensure all parties are compliant with the agreement. We are all for people keeping to the rules but this current proposition goes outside the agreement.”
The anti-Agreement Ulster Unionist MP Jeffrey Donaldson said he believed the outcome of the talks “would be rejected by the unionist community.” Donaldson said he wanted to see Sinn Fein excluded from government “until the IRA had completely disarmed and disbanded.”
In discussions this week in Dublin, the Irish government is believed to have made it plain to Sinn Fein that the deal agreed on in early March between the parties and both governments will not be renegotiated.
“The government is happy to provide clarification but the package will not be opened,” said a source close to the talks. It is believed that Dublin has finally drawn a line for Sinn Fein, and rejects further “incremental” negotiations. Irish minister Cowen warned parties against seeking “a concession too far.”
Meanwhile, the British government intends to introduce controversial clauses to the Northern Ireland Police Bill in London this week, enabling former paramilitary prisoners to sit on the new District Policing Partnerships.
They will not come into effect until a parliamentary order is passed recognizing that “acts of completion” by the IRA have taken place.
The SDLP leader, Mark Durkan, said that there is a need for progress in the next couple of weeks to restore people’s confidence in the political process. He said his party had outlined its concerns about the two governments’ proposals on sanctions.
In an renewed outbreak of sectarian violence six pipe bombs were thrown at St. Matthew’s church in the Short Strand and at elderly people’s homes in the same area. Loyalists also used a heavy earth-moving vehicle to destroy a security camera there.
Sinn Fein said it was a sinister development and people were worried it could be the prelude to a resurgence of the kind of street violence that plagued the area last year.
Meanwhile, the PSNI chief constable, Hugh Orde, has claimed a bitter split in the IRA’s ranks led to the murder of a man in South Armagh on March 12. Further bloodshed could follow the shooting of Keith Rogers close to the Irish border, he warned.
Orde confirmed his detectives were prepared for revenge strikes. “It clearly was a fall-out between two factions of the Provisional IRA. That sends a very worrying message to us.”
Jack Holland contributed to this story.