BAGHDAD — Iraqi government security forces on Saturday took back ground from protesters in Baghdad and Basra, in an apparent bid to quell the demonstrations that have lasted for nearly four months amid calls for new elections and an end to government corruption.

In Baghdad, security forces moved on two of the smaller protest sites and approached the central one, Tahrir Square, before falling back, but fired tear gas and bullets, wounding at least four. Across the country, at least four were killed and 13 injured on Saturday.

The government’s move to clear protesters came after the prominent Shiite cleric, Moktada al-Sadr, announced in a tweet on Friday that he was withdrawing support for the demonstrators and would no longer intervene on their behalf. He said his move was a result of what he called the antagonistic behavior of some of the protesters toward his followers.

His withdrawal of support, and the resulting departure of many of his followers from the demonstrations, deprived the protests of a critical base of participants, leaving those remaining more vulnerable to a government crackdown.