George Clooney's President Obama Fundraiser -- Release the Hounds!

Crap's getting REAL at Chez Clooney -- the LAPD Bomb Detection K-9 unit just showed up in full force.

As we reported, George Clooney's L.A. mansion is on mega-lockdown today while POTUS Barack Obama drops by for a $40,000-a-person fundraising event.

Law enforcement sources tell us, the U.S. Secret Service, the LAPD (including a special Counter Terrorist Unit), as well as the California Highway Patrol will all be present.