Conor Murphy condemned the double attack on police and put it down to a " sinister political element" against the party's policy on policing.

Stones, bottles and up to 30 petrol bombs were hurled at police twice last night by groups of youths in Crossmaglen.

No-one was injured, although fire and stone damage was caused to at least two vehicles.

Mr Murphy, who was at the scene until 10pm, today described the attacks as " unorganised" and claimed that those behind them only served to harm their own community.

"Our people were on the ground trying to get them to desist from the attacks," he said.

"I'm not sure it was well organised but I do suspect other influences there - political influences - but I can't say that for sure."

Mr Murphy said parents and the community safety group also weighed in in what they believed was a successful bid to stop the youths.

Another frenzied attack, however, resumed before midnight.

"Our presumption was that things had settle down by 10pm," said Mr Murphy. "I think a more sinister element returned later in the evening.

"Those people involved only did damage to their own community. Elderly people in the vacinity had to move out of the area that night."

Police were guarding the site of the Lynx crash on Sunday when they came under attack. Six people were hurt when the military helicopter came down in a field close to Lismore housing estate and the grounds of the Crossmaglen Rangers GAA club.

Mr Murphy said people in the community were "rightfully angry" at the attacks and encouraged co-operation with police.

"Information could be passed on to police," he said.

In earlier demonstrations in the area, an ambulance taking a casualty from the military aircraft to Daisy Hill Hospital was forced to stop after being ambushed by a group of youths.

Stones, fireworks and snowballs were hurled at the crew.

"They stopped the vehicle for about a minute and shone torches into it," the Ambulance Service's director of operations, Brian McNeill, said.

"We are only trying to do our job and it is difficult enough going to a major incident like that without having to deal with unruly crowds. And it is unacceptable."