EU leaders have expressed their shock at Monday’s deadly bomb attack at the Boston marathon, describing it as "atrocious" and "reprehensible".

“I condemn the appalling acts carried out in Boston and deeply regret the tragic outcome and loss of innocent lives. Those responsible for the atrocious acts will be brought to justice,” European Council President Herman van Rompuy said in a statement.

“My thoughts are with the victims and their families. The American people and authorities have the full sympathy and support of the EU,” he added.

EU High Representative Catherine Ashton said in a statement that she was “shocked to hear of the terrible bomb attack at the Boston marathon.”

“Such acts are reprehensible. We stand with the United States government and people in condemning this bombing,” Ashton declared.

Bulgarian EU Commissioner Kristalina Georgieva, responsible for humanitarian aid, said on Twitter: "Thoughts are with those in Boston today. Sad day."

Other European Commissioners also reacted to the tragic news on Twitter.