Five men have been arrested close to the Irish border in an ongoing operation against dissident republican activity.
Reports that shots were fired at detectives during an incident in the Omeath area of Co Louth are being investigated.
A Garda spokesman could not confirm other reports that the men were transporting explosives.
The five were travelling in three cars when they were stopped and detained.
They are being held under section 30 of the Offences Against the State Act.
A Garda spokesman said: "These arrests are part of an operation targeting dissident republican activity. The operation is very much ongoing at the moment."
Two men are being held at Dundalk Garda station, two at Drogheda Garda station and one man is being questioned at Balbriggan Garda station, in north Dublin.
The cars seized in the operation are being forensically examined.
Justice Minister Dermot Ahern said he was briefed by Garda Commissioner Fachnta Murphy today on the operation.
"I congratulated the Gardai on their work and their professionalism in at times difficult circumstances," he told the Press Association.
"I continue to take the threat from dissidents very seriously and we are working closely with the security services in the North.
"The Gardai and the Police Service of Northern Ireland are working very closely together, as is evidenced by what unfolded in the last 24 hours."
Mr Ahern met his Stormont counterpart Justice Minister David Ford yesterday at Carlingford, Co Louth, near where last night's incident unfolded.
The pair held talks about cross-border policing co-operation and a crackdown on cross border criminality.