The RUC Chief Constable, Sir Ronnie Flanagan, said the explosives seizure was evidence of the need for the security forces to "remain vigilant and maintain the capability to deal effectively with those who would threaten the community in Northern Ireland".
He was speaking after meeting a Democratic Unionist Party delegation at RUC headquarters in Belfast. The former Mid-Ulster MP, the Rev Willie McCrea, who headed the delegation, said the find had "very serious implications".
"We congratulate the security forces that they caught the culprits red-handed, but in addition to the Provisional IRA, which remains completely intact, we are now witnessing an increased threat to the law-abiding citizens of Northern Ireland by so-called republican dissidents. We regard this as a highly serious matter," he told The Irish Times.
The DUP Assembly member for South Armagh, Mr Paul Berry, said the explosives seizure strengthened unionists' case for an increase, rather than a reduction, in the British security forces presence.
"If this find had not been intercepted by the RUC last night, there could have been bloodshed today and I commend the RUC on the work which they carried out," he added.
His party colleague, Mr Sammy Wilson, said if the Irish foreign minister required any evidence as to why there was a continued need for the current level of security forces in Northern Ireland, "republicans have supplied him with 500lbs worth of it last night".
Mr Gerry Kelly, Sinn Fein Assembly member for North Belfast, said the discovery of the explosives and loyalist attacks were clear evidence that the political vacuum was being filled.
"If you want to deal with the decommissioning issue then you must deal with the causes of conflict."
The Shadow Northern Ireland Secretary, Mr Andrew Mackay, added his voice to calls for the suspension of the prisoner early release scheme.
"This graphically illustrates why the Conservatives have been right to demand that the prime minister stop early releases of prisoners whilst there is no decommissioning by paramilitaries," said Mr Mackay.