Washington (CNN) -- Congress delved Wednesday into the politically explosive issue of unmanned drone attacks, questioning the legality of operations increasingly used to combat al Qaeda and Taliban militants in countries such as Pakistan. In the eight years of George W. Bush's presidency, unmanned aircraft -- or drones -- attacked militant targets 45 times. Since President Obama took office, the numbers have risen sharply: 51 last year and 29 so far this year. Most attacks have targeted suspected militant hideouts in Pakistan. While the United States is the only country in the region known to have the ability to launch missiles from drones -- which are controlled remotely -- U.S. officials normally do not comment on suspected drone strikes.
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NEW: ACLU calls drone attacks part of illegal program for U.S. to target, kill terror suspects
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Since President Obama took office, number of drone attacks has risen
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U.S. law professors debate legality of such attacks during a House subcommittee hearing
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Biggest controversy: legality of strikes conducted by CIA, as opposed to U.S. military
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