In a worrying sign for King Abdullah II of how the country might witness outbreaks of violence, police seized a cache of weapons as they were being brought into the centre of the capital.
Eight men were arrested after they were caught smuggling guns and batons in three vehicles, a police spokesman told AFP.
In a last ditch effort to ward off the protestors, late on Thursday night the king announced the dissolution of the parliament and called for early elections, to be held by the end of the year.
But the opposition Muslim Brotherhood announced to the crowds of protestors on Friday that it would boycott the polls as it did in 2010 to protest the lack of reforms.
The demonstration was the largest in Jordan in years with an estimated 10,000 people gathering outside the Al-Husseini mosque.
The chants echoed those used by the demonstrators in neighbouring Syria in the early days of the uprising against President Bashar al-Assad 18 months ago: "The people want the reform of the regime".
Unlike the Middle East's toppled dictators, the king has sought to abate the flames of an uprising by avoiding force against demonstrators. At past rallies held by anti-government Salafists, soldiers have been known to distribute water bottles to the crowds. A counter-rally in support of the monarchy and its reforms that was expected to also draw thousands was cancelled on Friday in a move to see-off possible violent clashes.
Jordan's tolerance for opposition protests however wears thin when the calls pose a direct threat to the monarchy. To date as many as 15 activists have reportedly been detained for slandering the royal family.
