Gardaí have arrested four people following an armed robbery at a petrol station in Co Carlow.

It happened on the M9 shortly after 2.30am on Wednesday.

Two men, one armed with a gun and the other with a knife, entered a filling station at Tinryland and threatened staff.

One shot was fired during the course of the raid.

They made off in a dark-coloured Volkswagen Golf with a small sum of cash.

However no one was injured in the incident.

During a follow up operation shortly after 9.00am, investigating gardaí - assisted by the Armed Support Unit - carried out a search at a house in Carlow town.

Three men and one woman - all understood to be aged in their 20s - were arrested.

They are currently detained under Section 30 of the Offences against the State Act at Carlow station.

Gardaí are appealing to anyone in the filling station or the surrounding area between 2:00am to 2:30am to come forward.

Thye can contact Carlow garda station on 059-913-66220 or the Garda Confidential Line at 1800-666-111.

Gardaí say investigations are on-going.