Sudanese anti-coup protesters have taken to the streets in the capital Khartoum to reject the October 25 military takeover, the latest in a series of demonstrations that have continued even after the reinstatement of the prime minister.

Reuters news agency reported that Sudanese security forces fired tear gas and used stun grenades to try and break up the demonstrations by hundreds of thousands of people.

Demonstrations were also under way in other cities across the country to mark the third anniversary of protests that touched off a popular uprising that led to the overthrow of longtime President Omar al-Bashir.

On Saturday night, Prime Minister Abdallah Hamdok warned in a statement that Sudan’s revolution faced a major setback and that political intransigence from all sides threatened the country’s unity and stability.

Ahead of the protests, security forces sealed off major roads leading to the airport and army headquarters as well as most bridges connecting Khartoum to sister cities Bahri and Omdurman across the Nile River.

Al Jazeera’s Hiba Morgan reporting from Khartoum said that for a few minutes, protesters were able to reach the southern gates of the presidential palace, but were met with tear gas and live ammunition.

"A majority of them have been forced to retreat following a heavy amount of tear gas that has been fired by security forces,” Morgan said.

"The military who guard the presidential palace have also used live ammunition, according to protesters who ran away from the southern gates of the presidential palace.”

But protesters are still gathering on the road leading to the palace, Morgan said.

"Many of them are not far from the front gate.

"They say they’re here to voice their demands and show the military that they want a civilian rule and no amount of tear gas or live ammunition will take them away from their demands.”

Protesters chanted "the people are stronger and retreat is impossible”. Some demonstrators ran into side streets to shield from the tear gas.

Despite security forces blocking bridges into the capital, protesters were able to cross a bridge connecting the city of Omdurman to central Khartoum but were met with heavy tear gas, Reuters witnesses said.

Witnesses also told Reuters that protesters were trying to cross a bridge from Bahri, north of Khartoum, to the capital.

"The protesters are saying the revolution is incomplete because the military is still in power,” Morgan said.

"They are saying the military should go back to the barracks and that power should be handed to a civilian government. Many of them are saying they are not satisfied with the way the revolution has been going on over the past two years,” Morgan added.

Images shared on social media showed protests beginning in cities outside Khartoum, including Port Sudan on the Red Sea coast and El-Deain in the western region of Darfur.

It would be the ninth in a series of demonstrations against the coup that have continued even after the military reinstated Hamdok, who had been under house arrest, on November 21 and released him and other high-profile political detainees.

The Central Committee of Sudanese Doctors says 45 people have been killed in crackdowns on protesters since the coup.

The military and civilian political parties had previously shared power since al-Bashir’s removal. But the deal reinstating Hamdok faces opposition from protesters who had seen him as a symbol of resistance to military rule and denounced it as a betrayal.

Civilian parties, and neighbourhood resistance committees that have organised several mass protests, demand full civilian rule under the slogan "no negotiation, no partnership, no legitimacy”.

On Saturday night and early Sunday morning, people arrived in bus convoys from other states, including North Kordofan and Gezira, to join protests in Khartoum, witnesses said.

A rally on Friday by members of civilian parties, known as the Forces of Freedom and Change coalition, was broken up by tear gas from an unclear source as witnesses told Reuters there was no sign of security forces on the scene.