Three members of a gang who are suspected of involvement in over 100 burglaries hit a garda in a stolen 4x4 and broke his leg.
They also ploughed their vehicle into an unmarked garda patrol car.
The shocking incident happened shortly after midnight yesterday.
The garda car was written off in the collision and a garda armed response vehicle was also badly damaged.
The officer who suffered a broken leg was on foot when he was hit by the 4x4, and it is understood he continued to work even after suffering the serious injury.
Three men - aged 36, 38 and 39 - remained in garda custody last night.
They are two brothers and their cousin who are suspected of being key members of the burglary gang whose base is in the Mountrath area of Laois.
The ramming incident happened at Cloncourse, Co Laois, and it followed a detailed surveillance operation which was led by gardai from the Laois/Offaly division.
Sources have revealed officers were watching as the criminals went to retrieve the 4x4, which had been hidden in a bog nearby after being stolen in Nenagh, Co Tipperary, last week.
The vehicle was driven from the bog but failed to stop at a road checkpoint which was manned by armed Regional Support Unit officers and other gardai.
As well as injuring the Laois-based officer, the 4x4 crashed into the two other vehicles before the occupants fled on foot into a nearby field.
"Gardai quickly searched the area with the assistance of the Garda Air Support Unit and arrested the three men a short time later," a garda spokesman revealed.
One male officer was treated for back injuries and the suspects were brought to Portlaoise and Tullamore Garda Stations.
The spokesman added: "Four gardai received non-life threatening injuries during the incident and attended Midland Regional Hospital Portlaoise."
The gang who were targeted in the operation are suspected of a rural burglary crimewave all across the midlands and south east, and they have been targeting farms, farm suppliers and co-op shops, as well as veterinary practices, in at least six counties in recent months.
Gardai believe they are behind more than 100 burglaries since the start of the year.
"These are very significant arrests and more operations like this are planned in the coming weeks," a senior source told the Herald.
Gardai said that vehicles, trailers and farm equipment have been recovered during on-going searches yesterday.
"The modus operandi of this gang has been to steal a 4x4 vehicle and then use it to target farms and rural businesses, sometimes hitting more than three a night," the source added.