Details added (first version published at 00:51)
One protester was killed and 120 were wounded, including 58 police, when Jordanian security intervened to end clashes between two rival rallies at an Amman square, the Public Security Department said late Friday.
It was the first fatality in two months of demonstrations in Jordan that were inspired by the uprisings in Tunisia and Egypt, dpa reported.
Policemen used clubs and water cannons against the protesters and removed the tents they had erected overnight at Nasser Square in the centre of Amman, witnesses said.
The gathering, which called itself "March 24 Youth", was demanding reforms, including the dissolution of the lower house of parliament and the amendment of the constitution.
Government supporters attacked the group late Thursday, pelting them with stones and leaving 30 people injured. The mostly young demonstrators claim to have no political affiliation. They organized themselves via Facebook and other internet platforms.
"An autopsy proved that the fatality was due to a heart failure and there were no traces of beating on his body," General Hussein Majali, who heads of the Public Security Department, told a press conference.
"Most of the wounded have now left the hospital," he added. Majali said the fatality, a 55-year-old man identified as Khairy Saad, was among those gathered to express loyalty to King Abdullah II.
At least 10,000 people took part in a rally at King Hussein Park Friday to express loyalty to Abdullah and the ruling Hashemite family.
Majali said eight people had been arrested, including six from the "March 24 Youth" group and two from the other rally, described by protesters as hurling rocks on demonstrators, wounding at least 30.
"The security authorities have opened an investigation into the incident," he added.
Interior Minister Saad Srour said security forces were obliged to intervene to prevent the closure of key traffic points.
In an interview with state-run television Friday night, Prime Minister Marouf Bakhit said what happened was "painful and harmed Jordan's image which we struggled to preserve over the past weeks."
He vowed "while we will continue to show due respect to freedom of expression, we are not going to allow any gatherings that cut off traffic and cause any material damage for anyone."
Bakhit accused the Islamic Action Front (IAF) and the mother group, the Muslim Brotherhood movement, of being behind the rally at Nasser Square.
"We have convincing evidence that they were the organizers of the event, and I say to them now: stop playing with fire," he said, charging that Islamists "received instructions from groups in Egypt and Syria."
The Brotherhood and IAF last week decided to boycott a 53-member National Dialogue Committee formed by the prime minister to consider political reforms proposed by Abdullah, including election and political parties laws.
Islamists cited Bakhit's failure to include the amendment of the constitution on the panel's agenda as a reason for the boycott.
They also accused him of "rigging" the 2007 elections when he was prime minister to reduce their chances in the polling process.
"The door is still open for you to join the dialogue, otherwise I hold you responsible for the pattern of action you follow because it leads to sedition," Bakhit told Islamists.
"We are not going to accept dialogue that is conducted from the streets," he added, alluding to almost weekly rallies over the past three months.