Indonesia's parliament postponed ratifying changes to an elections law on Thursday amid protests in multiple cities, following outcry over legislation seen to strengthen the political influence of outgoing President Joko Widodo.

The plenary session to pass the changes was delayed due to a lack of a quorum, legislator Habiburokhman told reporters outside the parliament building.

It is unclear if parliament will reconvene to pass the law before the registration for regional elections opens next Tuesday.

The parliament planned to ratify changes that would have reversed a ruling by the constitutional court earlier this week.

The legislative changes would have blocked a vocal government critic in the race for the influential post of Jakarta governor, and also paved the way for Widodo's youngest son to run in elections in Java this November.

The power struggle between the parliament and the judiciary comes amid a week of dramatic political developments in the world's third-largest democracy, and in the final stretch of the president's second term.

Widodo downplayed the concerns, saying on Wednesday the court ruling and parliamentary deliberations were part of standard "checks and balances".

The home affairs minister said the changes were intended to provide legal certainty.

More than 1,000 demonstrators gathered on Thursday outside the parliament building in Jakarta and across multiple cities in Java, some holding banners accusing Jokowi of destroying democracy.

Authorities fired tear gas at demonstrators in Semarang, according to footage from Kompas TV.

"This is the peak of my disdain," said Afif Sidik, a 29-year-old teacher who joined the protest outside parliament.

"This is a republic. It's a democracy, but if its leadership is decided by one person, or an oligarch, we can't accept that."

Legal experts and political analysts have described the power struggle as bordering on a constitutional crisis.

Elections analyst Titi Anggraini characterised the manoeuvre as "constitutional insubordination".