Lieutenant General Hussein Majali told a news conference: “Fifty-one policemen, including senior officers, were stabbed with knives, beaten with bats or hit with sharp tools, while 32 other policemen were treated for tear gas inhalation”.

He said: “Eight civilians were also hurt when police fired tear gas and tried to stop Islamist Salafist demonstrators from attacking shoppers in Zarqa”, adding that 17 protesters were arrested and police are searching for more people.

“It was clear that the demonstrators had plans to clash with police. They carried swords and daggers and were provocative, seeking to drag police into a bloody confrontation.”

Earlier, police spokesman Lieutenant Colonel Mohammad Khatib told AFP six officers stabbed in today’s clashes were “in serious condition”.

He said police “had to fire tear gas after a group of Islamist Salafists attacked some citizens … accusing them of being atheists.”

The Salafists have been demonstrating over the past few weeks to demand the release of 90 Islamist prisoners, including Abu Mohammed al-Maqdessi, the onetime mentor of slain al-Qaeda in Iraq leader Abu Musab al-Zarqawi.

Zarqawi, who hailed from Zarqa in the country’s north, was killed in an air strike north-east of Baghdad in 2006.

The group has also called for the release of Mohammad Shalabi, better known as Abu Sayyaf, who was convicted on terrorism charges following riots in the restive southern city of Maan in 2002.

The Salafists espouse an austere form of Sunni Islam that seeks a return to practices common in the early days of the faith.

Meanwhile, more than 1000 people demonstrated in Amman after midday prayers, demanding “regime reforms”, Prime Minister Maaruf Bakhit’s ouster and the dissolution of parliament.

“The people want to reform the regime and eliminate corruption. Jordan is free; Bakhit, get out,” demonstrators chanted as they marched from Al-Husseini mosque in the city centre to the nearby city hall.

Holding large national flags, the protesters carried banners reading “the people want democracy and social justice” and “we want to dissolve parliament”.

The demonstration was organised by the powerful Muslim Brotherhood and its political arm, the Islamic Action Front (IAF), as well as leftist and other opposition parties.

“The demonstrations will continue until reforms are achieved,” Jamil Abu Baker, Brotherhood spokesman, told AFP.

“So far, we cannot see any (government) intention to carry out reforms. The people are determined to have real reforms and get rid of corruption.”

Hundreds of March 24 youth movement members, who were attacked last month by government supporters in clashes that killed one man and injured 160, held a sit-in outside the city hall, calling for general reforms and singing national songs.

About 200 policemen were deployed as dozens of government supporters gathered in the area.

Pro-reform demonstrations were held in other centres, such as Karak and Maan in the south, and Zaraqa and Irbid in the north.

On Thursday, the US embassy in Amman told Americans to avoid areas of protests, saying: “Even demonstrations intended to be peaceful can turn confrontational and possibly escalate into violence.”

Jordan has been the scene of three months of protests calling for political and economic reforms as well as the stamping out of corruption.