NEW : Petrol bombs hurled at police after arrests in connection with soldiers ' killings . two arrested over slayings of Three soldiers in Northern Ireland Monday . Three men also being held in last week 's killing of police officer . Two Catholic groups have reportedly claimed responsibility for the killings .
NEW : Petrol bombs hurled at police after arrests in connection with soldiers ' killings . Three arrested over slayings of two soldiers in Northern Ireland last week . Three men also being held in Monday 's killing of police officer . Two republican groups have reportedly claimed responsibility for the killings .