It is the 10th day of major demonstrations since an October 25 coup, with protests continuing even after Abdallah Hamdok was reinstated as prime minister on November 21. The demonstrators have demanded that the military have no role in government during a transition to free elections.
In neighbouring Omdurman on Saturday, security forces also fired tear gas at protesters around 2 km away from a bridge connecting the city to central Khartoum, another Reuters witness said.
Internet services were disrupted in the capital, Khartoum, and soldiers blocked roads early in the day, the witnesses said.
Locals were also unable to make or receive calls domestically.
Despite the internet being cut off, people were still able to post on social media, with images showing protests taking place in several other cities, including Madani and Atbara.
At the same time, soldiers and Rapid Support Forces were out in force blocking roads, leading to bridges linking Khartoum with Omdurman, its sister city across the Nile river, they said.
The SUNA state news agency reported that the province of Khartoum closed bridges on Friday evening in anticipation of the protests.
“Departing from peacefulness, approaching and infringing on sovereign and strategic sites in central Khartoum is a violation of the laws,” SUNA reported, citing a provincial security coordination committee.
“Chaos and abuses will be dealt with,” it added.
Protesters in Khartoum chanted: “Close the street! Close the bridge! Burhan will come straight to you,” referring to military leader and sovereign council head Abdel Fattah al-Burhan.
They were also heard cheering when security forces fired tear gas, according to a Reuters witness.
A senior official at one internet provider told Reuters the service disruption followed a decision by the National Telecommunication Corporation, which oversees the sector.
United Nations special representative to Sudan Volker Perthes urged Sudanese authorities not to stand in the way of Saturday’s planned demonstrations.
“Freedom of expression is a human right. This includes full access to the internet. According to international conventions, no one should be arrested for intent to protest peacefully,” Perthes said.
The military could not immediately be reached for comment.
A march planned for Saturday is due to converge on the presidential palace and the demonstration will end at 5 pm (1500 GMT), organisers say.
In Darfur, governor Minni Minnawi asked citizens to stop looting the offices of UNAMID peacekeepers late on Friday, with sources telling Reuters they heard gunshots in the vicinity on Saturday morning.
Last Sunday, hundreds of thousands of people marched to the presidential palace and the security forces fired volleys of tear gas and stun grenades as they dispersed protesters who had been trying to organise a sit-in.
Forty-eight people have been killed in crackdowns on protests since the coup, the Central Committee of Sudanese Doctors said.