Former premier and intelligence chief Ahmad Obeidat joined thousands of Jordanians on Friday to protest fuel price hikes, demanding regime reform and the resignation of Prime Minister Abdullah Nsur.
"The people want to reform the regime. We demand reform and change. Nsur, out before the people revolt," chanted the protesters led by Obeidat's National Reform Front which includes opposition Islamists.
"The people want the downfall of the (fuel) prices. Together, let's reject the decision to raise the prices," read a banner carried by the demonstrators, gathered near Gamal Abdel Nasser Circle, close to the city centre.
Police said 3,000 people took part in the protest, while Islamists put the number at around 20,000. According to an AFP estimate, the demonstrators numbered around 10,000.
Demonstrators gave police flowers, but a limited number called for "the fall of regime," which is punishable by imprisonment under Jordanian law.
Obeidat however stopped them.
"We did not come here today to flex muscle. We came here to defend our constitutional rights. We will stick to our demand of reforming the regime," he told the crowds.
"We want comprehensive reform. We insist on rejecting the general election and any polls under this current bad electoral law."
The National Reform Front and Muslim Brotherhood have said they will boycott Jordan's January 23 vote.
Earlier in November, the government raised fuel prices by up to 53 percent, sparking a series of nationwide protests, rioting and clashes that killed one person and wounded dozens.
Nsur, who formed his government on October 11, has defended the price hike as "unavoidable" given Jordan's $5-billion (3.9-billion-euro) budget deficit and said the measures would save $42 million by year end.
Jordanians have held Arab Spring-inspired protests since last year, demanding reforms and a tough anti-corruption fight.