Anti-terrorist detectives were questioning nine suspected Irish Republican Army dissidents Monday over this month's deadly gun attacks on British soldiers and police.

Sinn Fein deputy leader Martin McGuinness, the former IRA commander who is now the senior Irish Catholic in Northern Ireland's power-sharing government, said he was confident the community was uniting against the rising dissident threat.

"People are not shaken, they understand this is an attempt to create mayhem in our society. It isn't going to succeed," McGuinness told reporters during a visit to New York City.

The dissidents are trying to undermine the IRA's 2005 decision to renounce violence and disarm and Sinn Fein's efforts to persuade Catholics to cooperate with the police force — once overwhelmingly Protestant but now more than 25 percent Catholic.

The nine suspects arrested last week are suspected of involvement in either the March 7 attack on the Massereene army barracks in Antrim, west of Belfast, or the March 9 killing of a policeman in an Irish nationalist district of Craigavon, southwest of Belfast.

The nine include two well-known Irish republicans detained Saturday. The arrest of Colin Duffy, 41, triggered weekend riots by his largely teenage supporters in the town of Lurgan. Police also arrested Declan McGlinchey, 32, son of Dominic "Mad Dog" McGlinchey, who once boasted of killing more than 30 people as leader of an IRA splinter gang called the Irish National Liberation Army. Former INLA colleagues killed him in 1994 in front of his son.

In the March 7 attack, two masked men with assault rifles fired more than 60 rounds at off-duty, unarmed soldiers collecting pizzas from two delivery men outside their base. Two soldiers died and four other people were seriously wounded, including both pizza couriers. A splinter group called the Real IRA claimed responsibility.

Two days later, a 48-year-old policeman was shot in the head after his unit responded to an emergency call from a woman whose home was being attacked by stone-throwing youths. The Continuity IRA claimed responsibility.

Analysts say the dissidents — who have mounted more than 20 gun, bomb and rocket attacks since late 2007 — hoped this month's killings would undermine the current U.S. visit of McGuinness and Peter Robinson, the Protestant leader of the power-sharing government.

The two leaders twice delayed their trip last week because of the killings, but are expected to meet President Barack Obama at the White House and congressional leaders on Capitol Hill on Tuesday, St. Patrick's Day, an annual event cherished by Ireland's leaders north and south.

Authorities are tightening security measures in Northern Ireland. Police have asked private security firms to take over some duties, including locking security gates at the medieval walls in Londonderry each night, amid fears dissidents might ambush police.

The British army canceled a planned Belfast parade for troops returning from Iraq next month. A similar parade in November triggered brief street clashes between Protestants cheering the soldiers and Catholics protesting their presence.