The murders of two soldiers in Northern Ireland will not derail the peace process, Gordon Brown has insisted. The Prime Minister sent his condolences after gunmen opened fire outside Massereene Barracks in Antrim on Saturday night. Mr Brown said: "I can assure you that we will bring these people to justice." Mr Brown branded the attack "cowardly", adding: "Our first priority has always been the safety of people in Northern Ireland, and we will do everything in our power to make sure that Northern Ireland is safe and secure. "No murderer will be able to derail the peace process, that has the support of the vast majority of the people of Northern Ireland. We will step up our efforts to make the peace process one that lasts and endures." The victims were understood to be taking delivery of a pizza when the attackers pulled up in a vehicle and opened fire. Four other people were seriously injured, including the two pizza delivery men. No one has yet claimed responsibility for the shooting, but dissident republicans opposed to the peace process were immediately blamed. Police are understood to be examining a car found abandoned in the nearby town of Randalstown. Officers are trying to establish whether the vehicle was used in the shooting. The incident happened just 36 hours after Northern Ireland Chief Constable Sir Hugh Orde confirmed that undercover soldiers had been called in to carry out surveillance operations on dissidents amid warnings that the threat against his officers and military personnel was at its highest for almost a decade. The gunmen's car or van pulled up outside the barracks' main gates shortly before 10pm while soldiers and security staff were taking delivery, it is understood. Secretary of State for Northern Ireland Shaun Woodward condemned the shooting as an "act of criminal barbarism". He said: "The contrast between those who serve the community and those who would destroy it could not be clearer. "The people who did this will be pursued and they can be assured that they will never be able stop political progress in Northern Ireland." Witnesses reported hearing two long busts of gunfire as a car drove by the barracks - home to 38 Engineer Regiment. At least six ambulances and three paramedic vehicles rushed to the scene as emergency sirens blared from inside the complex.