A bomb destroyed a bridge in Northern Ireland late on Saturday in an attack police said was targeted at its officers.
The blast happened on a country road near the south Armagh border. No one was injured. It came as police in the Republic of Ireland questioned five men as part of a probe into dissident Republican militants active in Northern Ireland.
Police chief superintendent Alisdair Robinson said the explosion was "a totally reckless act that could easily have led to loss of life if anybody had been driving past at the time."
"However I believe at this stage the real target was my officers. This was an attempt to lure police into the area to injure or kill them," he said.
A 1998 peace agreement largely ended three decades of violence between predominantly Catholic groups who want a united Ireland and mainly Protestant unionists who want Northern Ireland to remain part of the United Kingdom.
The main paramilitary organisations on both sides, such as the Provisional IRA, have surrendered their weapons, but militant splinter groups have stepped up attacks recently.
Dissidents have attacked security forces several times, with the Real IRA believed to be leading much of the campaign including car bombings and shooting at police officers.
The bridge attack took place ahead of a day of parades on Monday by the pro-British Orange Order, made up of Protestants who want Northern Ireland to remain a British province.
The marchers, who wear orange sashes and bowler hats to commemorate a 17th century victory of Protestants over Catholics, cause tension each year with the Catholic minority, many of whom would like to see a united Ireland.
Last year, nationalist rioters attacked police with bricks, bottles and other missiles on the day.
