Dissident republicans: Dealing with upsurge in terrorist activity 21 November 2014 Last updated at 18:06 By Vincent Kearney BBC News NI Home Affairs Correspondent The taxi driver thought it was just another routine fare. It was far from it. He was driving towards Belfast's Falls Road on Thursday night when his cab was stopped close to Grosvenor Road police station, shortly after 22:00 GMT. His 29-year-old male passenger was arrested. Police found an AK47 assault rifle and ammunition in a hold-all bag. In a follow-up operation nearby in west Belfast on Friday morning, the police arrested three more men, aged 27, 29 and 46. They are all being questioned at Antrim police station. One of the four men arrested is also being questioned about a rocket attack on a police Land Rover in the Ardoyne area of north Belfast on Sunday night. Dissident republicans released a propaganda photo of a homemade rocket launcher they said was used in Sunday's attack. The photo was given to the Irish News. The device hit the PSNI vehicle and caused some damage, but did not penetrate the armour. The man who fired it dropped the launcher before running off and it is now being examined by forensic scientists. Detectives are studying footage from CCTV cameras in the area that are believed to have recorded what happened. The attack came two weeks after a number of police officers in Londonderry escaped injury when a homemade mortar hit their vehicle as they drove through the Creggan area of the city. There have been a series of peaks and troughs in dissident republican activity in recent years, and police will be concerned about the recent upsurge. But there has also been an upsurge in activity by the Police Service of Northern Ireland (PSNI) and M15. Huge undercover resources are deployed to monitor the activities of dissident suspects, and to thwart planned attacks. The latest arrests came just three days after seven men appeared in court as the result of a major police investigation into the activities of the Continuity IRA. They were among 12 men arrested at a house on the outskirts of Newry, County Down, on 10 November. It was revealed that listening devices planted by MI5 enabled the police to gather around 70 hours of secret recordings, dating back to August this year. Separately, police in the Republic of Ireland seized guns and bomb making material during searches at three locations in Dublin last weekend. They described the seizures as a "major setback" for dissident republicans. While the police will be concerned about the current spike in dissident republican activity, dissidents will be concerned about the level of infiltration within their ranks.