Northern Ireland police on Tuesday reported a string of bomb scares and carjackings in Belfast overnight, blamed on dissident republicans linked to the killings of two soldiers and a policeman.

A series of abandoned and burning vehicles caused security alerts, while several police stations were closed because of bomb scares and a hotel next to the Stormont Parliament was evacuated, police said.

There was also a series of carjackings and 350 children at a primary school in Belfast were sent home on Tuesday after a suspicious object was found nearby, the BBC reported.

Local politicians blamed the disruption on dissident republicans making a show of force after the shooting of two British soldiers at an army barracks and a police officer within 48 hours of each other this month.

They were the first such killings for roughly a decade and threatened to disrupt the peace that has reigned in Northern Ireland since a 1998 peace accord which largely ended 30 years of civil unrest.

"The criminal terrorists responsible for the series of bomb scares and hijackings are beneath contempt and have no support whatsoever in the community," said Northern Ireland's First Minister Peter Robinson.

"In recent weeks, Northern Ireland has sent these murderers the message loud and clear. We will not be dragged back into death and mayhem," said Robinson, the leader of Northern Ireland's Democratic Unionist Party (DUP).

The scares were also condemned by the main republican party, Sinn Fein, which is part of Northern Ireland's devolved government and has also spoken out against the killings.

"I would like the spokespeople of those behind these alerts to come forward and explain how this will in any way achieve a united Ireland," said Sinn Fein lawmaker Caral Ni Chuilin, referring to the party's main goal.

Irish Foreign Minister Micheal Martin, describing the acts as "criminal" and "devoid of purpose", denounced those responsible.

"They are the enemies of republicanism," Martin said. "This tiny minority are defying the spoken will of the people. They have no support beyond their ideological and physical ghettos."

European Commission chief Jose Manuel Barroso also said he was "very concerned" by the "worrying" violence ahead of a meeting with Robinson and his deputy, Sinn Fein's Martin McGuinness.

Experts said the scares marked a return to tactics used during the three decades of civil unrest known as the Troubles by republicans wanting to disrupt the British province's economy.