BAGHDAD — Iraq's top Shiite cleric says the government must show it is seeking genuine change to combat corruption and not just introduce temporary measures to placate the embattled nation.

In a message delivered by a representative in a Friday sermon, Grand Ayatollah Ali al-Sistani also cautioned protesters who have staged weekly rallies to press demands for reform. He warned against groups seeking to hijack their movement to further other interests.

The comments, delivered in the holy Shiite city of Karbala south of Baghdad, came just hours before thousands of Iraqis were scheduled to rally in Baghdad and a string of other cities to demand better services and an end to corruption.

Followers of a radical, anti-American Shiite cleric, Muqtada al-Sadr, are expected to join the rally in Baghdad's central Tahrir square.