BAGHDAD, April 2 -- An influential Shiite Muslim cleric whose newspaper was shuttered for printing inflammatory articles called Friday for his followers to strike back at officials and appointees of the U.S.-led occupation authority.

"I and my followers of the believers have come under attack from the occupiers, imperialism and the appointees," Moqtada Sadr said in a sermon in the southern town of Kufa, outside the holy city of Najaf. "Be on the utmost readiness, and strike them where you meet them."

On Friday evening, clashes erupted in Kufa. Residents said that rocket-propelled grenades and mortars were fired but that it was unclear who was involved. At some point in the fighting, gunmen killed Kufa's police chief, Col. Saeed Tiryak, and a colleague, according to Iraqi police sources quoted by the Reuters news agency...

Reflecting the political rivalry between Shiite Muslims and Kurds -- two newly empowered groups that had been suppressed under Hussein's government -- Sadr issued a blunt warning to the Kurds.

"Stop supporting the occupation and the West," he said. "There will be a day when you'll be killed by their hands."

Sadr also threw his support behind two militant organizations: Hezbollah, based in Lebanon, and Hamas, based in the Palestinian territories. "From here, I declare my solidarity with the solidarity between Hezbollah and Hamas," Sadr said. "May they consider me their striking hand in Iraq, whenever necessity requires it."