Dissident republican terrorists have claimed they used newly-imported Semtex during a murder attempt on police officers.
The improvised mortar was launched at a passing PSNI Land Rover in west Belfast.
Activated by a command wire, the explosive contained recently acquired military-grade Semtex, according to those responsible.
If true, it would mark an extremely worrying development regarding the terror capacity of dissident groups.
But security sources have played down the claim saying there is no evidence of any new batches of the deadly explosive having entered Northern Ireland.
The resurgence of Semtex, tonnes of which was provided to the Provisional IRA by Libyan dictator Colonel Gaddafi in the 1980s, would be a significant escalation by dissidents.
Claims of such a development have been treated with scepticism, however.
Recently a senior police officer told this newspaper he was confident no new supplies of the plastic explosive were in the hands of dissidents.
"They are using improvised explosives and there doesn't seem to be military grade material available," the officer said.
"Their Semtex is all of a certain age and, given that there has been a decommissioning process, it can only be a diminishing resource.
"Last year the Guards seized 16 or 17 kilos of it and they haven't been able to replenish abroad. You need a very sophisticated network to be able to supply yourself with heavy military grade equipment – they haven't got one."
Hours prior to Friday night's attack off the Falls Road, a bomb was discovered on Blacks Road.
It is believed the under-car booby-trap device had fallen off the vehicle of a serving PSNI officer.
In a third incident in three days, a crude bomb was found in a residential area.
It was discovered between two train stations, in the Donegall Avenue area of south Belfast.
The alert between Great Victoria Street and Adelaide Halt resulted in the line being closed from Sunday evening until the early hours of yesterday.
The Police Federation, which represents almost 7,000 PSNI officers here, warned all of the force's staff to be extra vigilant because of the incidents.
Policing Board member and DUP MLA Jonathan Craig said dissident groups, namely Oglaigh na h'Eireann, the new IRA and Continuity IRA, remained intent on bloodshed.
"The dissident movement is now trying to score what they would see as a victory, that is murder and mayhem.
"These people are rebels without a cause," he said.
STORY SO FAR
A Filipino family was treated for shock after their vehicle was damaged by debris during Friday night's attack. The bomb was launched from the City Cemetery as a police patrol passed at around 10.30pm. The explosion was heard across Belfast.