Around 1,500 Jordanians, mostly Islamists, marched on Friday to reject a controversial electoral law, a day after the Muslim Brotherhood decided to boycott early polls expected later this year.
"We demand a democratic electoral law. We want to change the constitution and fight corruption," read a banner carried by the protesters in central Amman.
"The people want the downfall of the electoral law. If change does not happen, revolt is the solution," they chanted as they carried a large national flag.
The Brotherhood's shura advisory council voted on Thursday to boycott parliamentary elections because of "lack of political reform."
"We have decided the boycott because we did not want to be part of a conspiracy against reform," said Salem Falahat, a top dovish Brotherhood leader.
He saluted "tribes and political parties who want to boycott the vote."
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Other pro-reform demonstrations were held in southern and northern Jordan.
Under the controversial electoral law, voters cast two ballots: one for individual candidates in their governorates and one for parties nationwide.
King Abdullah II has ordered parliament to increase seats reserved for party candidates, urging the Islamists to take part in the polls.
MPs raised the number from 17 to 27, failing to satisfy opposition groups, including the National Reform Front, headed by former prime minister and intelligence chief Ahmad Obeidat, who said they plan to boycott the elections.
Some analysts have warned against "official rigging" of elections and growing political problems under this "exclusionary" law, saying it would be meaningless to hold the polls without the Islamists.
The Islamists boycotted early elections in 2010 in protest over constituency boundaries, saying the results over-represented loyalist rural areas at the expense of urban areas seen as Islamist strongholds.
Jordanians have held weekly pro-reform protests since last year, and the Islamists have repeatedly demanded sweeping changes that would lead to a parliamentary system in which the premier would be elected rather than named by the king.