The Ulster Unionist leader, Mr David Trimble, has blamed republican inaction on decommissioning for his decision to withdraw his three ministers from the Executive.
The Northern Secretary, Dr John Reid, said he was "disappointed but not surprised" by yesterday's developments. "I believe there is still hope that the Executive can be fully restored and all remaining parts of the Good Friday agreement implemented.
"I now intend to consult with the Irish Government and others before reaching a decision on the best way forward," he concluded.
The resignations took effect at midnight. Mr Trimble said if the IRA "commenced the process of actual decommissioning in a meaningful and verifiable manner", UUP ministers could be reappointed immediately. He was, however, disgusted at republicans' "cheek" in assuming Ulster Unionists would not act, he added.
"The Ulster Unionist Party has sustained the inclusive Executive for 18 months without any action by republicans on decommissioning. The UUP has honoured every single commitment entered into with the other signatories to the agreement, but our effort and good will has not been reciprocated."
Mr Trimble said the IRA had not only failed to decommission but continued to engage in violence in the shape of so-called punishment attacks. "This is therefore a blatant breach of the terms of the agreement and the standards required of a movement which has members holding ministerial office," he concluded.
The SDLP's Finance Minister, Mr Mark Durkan, who is to become party leader next month, said that in the wake of the UUP ministers' resignation - which will automatically be followed by those of the two DUP ministers - goings-on at Stormont were bound to be surrounded by an air of "ambiguity and absurdity".
Mr Durkan said he did not want to contribute to the impending crisis with recriminations. "I hope that the Secretary of State will not do anything premature, such as a reflex suspension. We can still hear from Gen de Chastelain the sort of development which we need to hear from him.
"There are still ministers carrying out their duties today and tomorrow and next week. In doing so they will serve the whole community . . . It is a real pity that we are losing five ministers who have been doing very good jobs, and that includes even the two DUP ministers."
The fact that the UUP's junior minister, Mr Dermot Nesbitt, remained in office resembled a situation where "the manager has taken his players off the pitch but has left the mascot", Mr Durkan added.
Sinn FΘin's chief whip, Mr Alex Maskey, said the responsibility for the latest crisis lay firmly with Mr Trimble.