The source of the explosions was not immediately clear, but the gunfire appeared to signal a fourth night of U.S. and European air operations over Libya on Tuesday to enforce a no-fly zone.
In the previous night's operations, the coalition air campaign suffered its first loss with the crash of an American fighter jet in the rebel-held east. Both crew ejected safely as the aircraft spun from the sky.
The no-fly zone is intended to protect civilians from attack by forces loyal to Moammar Gadhafi in their battles with rebel fighters. The uprising against Gadhafi's four-decade rule began Feb. 15.