WASHINGTON ( CNN ) -- Insurgents ' use of roadside bombs has increased dramatically in Afghanistan this year , according to Pentagon statistics , and the United States ' top military official is calling them the `` No . 1 threat '' to troops there . An IED is exploded by U.S. Marines near the remote village of Baqwa , Afghanistan , in March . In June there were 736 incidents in Afghanistan involving roadside bombs , called improvised explosive devices or IEDs , and 82 `` effective attacks , '' ones that caused casualties among coalition forces , the figures show . That was up from 263 incidents and 25 effective attacks in February , with the numbers increasing each month , said the Pentagon 's Joint Improvised Explosive Device Defeat Organization , an agency dedicated to thwarting roadside bombs . The number of coalition forces killed and wounded by such bombs has climbed , though not steadily , from 18 killed and 33 wounded in February to 23 killed and 166 wounded in June , the agency said . No numbers were provided for July , but such attacks have continued this month . In the latest , roadside bombs killed two NATO-led troops on Thursday , one in eastern Afghanistan and the other in southern Afghanistan . The military has called IEDs the weapon of choice for insurgents in that country . And at the National Press Club on Wednesday , Adm. Mike Mullen , chairman of the Joint Chiefs of Staff , said in response to a reporter 's question that the biggest threat to coalition troops in Afghanistan is improvised explosive devices . Watch Adm. Mullen address efforts in Afghanistan » . He noted that they `` have become more and more sophisticated over time '' and that they are being combined with `` more and more sophisticated attacks from the Taliban , where they use IEDs as well as other tactics to inflict or to fight our troops . ''
Pentagon agency : The U.S. Department of Defense has been using a program called the National Counterintelligence Resource Center (NCRRC) to collect and analyze information on foreign spies, according to documents obtained by WikiLeaks from whistleblower Edward Snow@@ Military has called IEDs the weapon of choice for insurgents in Afghanistan . No numbers were provided for July , but such attacks have continued this month .