Police investigating the murder of Pc Ronan Kerr have arrested a man and made one of the most significant arms discoveries for years.

Kalashnikov rifles, rocket launcher components and possibly Semtex explosive were discovered on Tuesday night in east Tyrone, police said.

The arrest of a 26-year-old man in Scotland yesterday came as the funeral of the Catholic officer heard a plea for an end to violence from Ireland’s most senior Catholic churchman Cardinal Sean Brady and as huge crowds rallied in Belfast demanding peace.

Pc Kerr, 25, died when an under-car booby trap bomb exploded in Omagh, County Tyrone, on Saturday. The murder has been blamed on dissident republicans opposed to the peace process and is believed to be aimed at deterring Catholics from joining the police.

Cardinal Brady said: “The people have said no, never again, to the evil and futility of violence.”

Police Service of Northern Ireland Assistant Chief Constable Drew Harris said: “Detectives from Serious Crime Branch who are investigating Ronan’s murder have made a significant discovery of arms and munitions – one of the most significant in recent years.”

The man arrested in Renton, Dunbartonshire, in connection with the find of weapons “is being brought back to Northern Ireland for questioning”, he said. The seizure was made in a garage on the Mountjoy Road, Coalisland.

The haul found in stolen vehicles included four rifles, ammunition, timer power units, detonators, incendiary bombs, components for rocket launchers and other explosive devices, and a quantity of explosives, possibly Semtex.

Mr Harris added: “This investigation into Ronan’s murder will continue in the coming days and weeks with the same determination and professionalism which resulted in last night’s discovery.”

Cardinal Brady said the people rejected those blamed for killing the new recruit.