Army special forces units are operating in a republican dissident stronghold of Northern Ireland, it was alleged tonight.

Republican Sinn Féin, political allies of the Continuity IRA, have claimed masked undercover soldiers have been carrying out surveillance on two housing estates in Lurgan, County Armagh in recent weeks.

They claimed the men were scouting the areas in white civilian vans. Republican Sinn Féin said the soldiers belong to the Special Reconnaissance Regiment.

The alleged presence of SRR soldiers – formerly known as the 14th Intelligence Unit – is controversial because British troops are meant to have been pulled off the streets, especially in nationalist areas.

Martin Duffy, press officer of Republican Sinn Féin in Lurgan, said the sightings of the elite military unit should be seen as part of a wider strategy to suppress "republican resistance" in the north Armagh area.

Duffy said that 14 of the 24 Continuity IRA prisoners held in the top-security Maghaberry prison outside Belfast are from the Lurgan area. As well as being subjected to surveillance, Duffy said that the prisoners' relatives and friends have been subjected to drug searches by sniffer dogs during visits. He also claimed that under the stop and search powers of Article 44 of the Terrorism Act hundreds of mainly young people have been stopped and searched.

"In the Lurgan area we are selling up to 600 copies of Republican Sinn Féin's newspaper Saoirse a month. Support for republican resistance is high in Lurgan and Craigavon especially among the young people. So it is not a surprise the Brits and the RUC/PSNI are targeting our areas.

"On the Tullygalley estate a couple of weeks ago, a white van was spotted going around the area. When it reached the back of the local youth centre, men in boiler suits, armed with rifles and wearing ski masks got out. They were not members of the republican movement. Nor were they ordinary police or British soldiers. They wore no uniform or had any badge markings. We believe they were the SRR brought in to intimidate republicans."

The housing estates of nationalist north Lurgan have been the focal points for rioting, bomb attacks on the Belfast to Dublin rail line and shootings at police patrols over the past 12 months.

One of the men who visited a relative in Maghaberry a fortnight ago said that he was strip-searched after being threatened with arrest. Gerard (not his real name) said he was forced to strip naked and then pin himself against a wall where police officers made him lift each leg up so they could even inspect his anus. A PSNI spokesman said the police could not comment on the alleged presence of military units.

Republican Sinn Féin's Geraldine Taylor, a one-time ally of Gerry Adams and now an opponent of the peace process, predicted there would be protests in the jail over the use of sniffer dogs.