The number of roadside bombs in Afghanistan has jumped 80 percent so far this year, and the devices are the leading killer of NATO and U.S. troops in the country, officials said Thursday.

According to an Associated Press report, Canadian Brig. Gen. Richard Blanchette, a spokesman for NATO’s International Security Assistance Force, the figures include both bombs that were detonated and bombs that were found by forces before they could be triggered by militants.

More than 30 U.S. troops have been killed by improvised bombs so far this year, according to Pentagon statistics.

In all, Blanchette said, improvised explosives account for around 60 percent of all troop deaths in Afghanistan.

Blanchette said many of the bomb components are transported in by militants in Pakistan.

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