A shrine in Tripoli venerating a Sufi Muslim saint was partly destroyed by men with bulldozers on Saturday. Residents said they were unimpeded by police.
The tomb of Sufi scholar Abdullah al-Sha'ab was outside the Sha'ab mosque, which had almost 50 Sufi graves inside.
The tomb of Abdel Salam al-Asmar, a Sufi scholar in the city of Zlitan, about 160km south-east of Tripoli, was damaged on Friday.
A library in a nearby mosque was also set on fire.
Hardline Salafists regard the shrines as idolatrous.
Video images showed chunks of masonry littering the floor, bullet holes pockmarking the walls and ornate Islamic tiling destroyed.