Sudanese security forces fired tear gas to disperse thousands of protesters who gathered on Monday, some burning car tyres, to mark the anniversary of a transitional power-sharing deal with demands for quicker political reform.
The agreement set up a precarious alliance of civilian technocrats and military officials following the April 2019 ouster of long-time ruler Omar al-Bashir, with elections due to be held after 39 months.
The government says it is pushing ahead with reforms, but many people want swifter and deeper change.
Protesters from neighbourhood-based "resistance committees" gathered outside cabinet headquarters in downtown Khartoum to voice their demands amid a heavy security presence.
The Sudanese Professionals Association (SPA), which spearheaded anti-Bashir protests and helped strike the deal with the military, said on Twitter that security forces violently dispersed protesters after they demanded to meet Prime Minister Abdallah Hamdok and refused an envoy sent in his place.
A Reuters witness saw large amounts of tear gas being fired.
The neighbourhood committees say they want to see the long-delayed formation of a transitional legislature, the reorganisation of the civilian Forces of Freedom and Change coalition and a civilian takeover of military-run companies.
They warned that Monday's demonstrations were just the start.
In a statement on Monday, Hamdok called for political and popular support for reform.
"The state apparatus needs to be rebuilt, the legacy of (the old regime) needs to be dismantled and the civil service needs to be modernized and developed to become unbiased between citizens, as well as effective," he said.
Hamdok, a former UN diplomat, has also launched peace talks with rebels in Darfur and other restive regions to end years of bloodshed, a key demand for protesters and a top priority for the government.
A deal is expected to be initialled on Aug. 28, Sudan's state news agency SUNA reported, citing Tut Gatluak, South Sudan's presidential envoy on security.