Gardaí were alerted to 196 incidents involving potentially lethal grenades, bombs or improvised explosive devices last year, the equivalent of almost four a week, new figures show.

Sixteen such incidents were also recorded in the first month of this year, leading to three arrests so far, according to the Minister for Justice, Dermot Ahern.

Responding to an oral question from the Labour party, Ahern revealed that updated Garda records show a total of 196 incidents involving grenades, bombs or improvised explosives in 2009.

He said there have been a total of 92 arrests in relation to these types of offences in the past two years, resulting in four convictions.

"In another 59 cases, the matters are currently before the courts or files are with the DPP," he said.

Opposition politicians have previously claimed the ability to use explosive devices indicates that former Republican terrorists are using their expertise to assist gangland figures. Recent incidents involving explosives include the discovery of a device outside a house in Drimnagh, south Dublin last month. A day later a second such device was also found at a flats complex on Clanbrassil Street in Dublin's south inner city.

Previous figures released by the defence forces showed that the number of incidents dealt with by the army bomb disposal squad last year rose by 45%.