Dozens of people have been injured as ultra-conservative Salafist Muslims clashed with pro-government supporters in Jordan’s northern city of Zarqa.
The police used tear gas to disperse the crowds, a police spokesman said. Six officers were stabbed and 34 others injured in the clashes, he added.
Meanwhile, up to 1,000 people protested in the capital Amman, calling for political and economic reform.
Opposition groups want free and fair elections and an end to corruption.
"[The police] had to fire tear gas after a group of Islamist Salafists attacked some citizens following their demonstration in Zarqa, accusing them of being atheists," spokesman Mohammad Khatib told the AFP news agency.
The Salafists have been demonstrating over the past few weeks to demand the release of 90 Islamist prisoners.
They include Abu Mohammed al-Maqdessi, the former mentor of slain al-Qaeda leader in Iraq, Abu Musab al-Zarqawi, who was born in Zarqa.