Sudanese anti-coup protesters are planning mass demonstrations Saturday against a military takeover that has derailed the country's transition to civilian rule and triggered deadly clashes.

The power grab has sparked a chorus of international condemnation, with the US and the United Nations urging Sudan's military leaders to show restraint.

General Abdel Fattah al-Burhan -- Sudan's de facto leader since the 2019 ouster of veteran autocrat Omar al-Bashir after huge youth-led protests -- led Monday's takeover.

He has dissolved the country's civilian-led government, ordered the detention of a number of top civilian officials and declared a nationwide state of emergency.

At least eight protesters have been killed and some 170 wounded in clashes with security forces, who have fired tear gas, live rounds and rubber-tipped bullets, according to medics.

Several pro-democracy activists have been arrested.

But on the eve of Saturday's rallies, a US official put the death toll at between 20 and 30, adding that the protests will be a "real test" of the intentions of Sudan's military.

"We call on the security forces to refrain from any and all violence against protesters and to fully respect the citizens' right to demonstrate peacefully," the official said in Washington on condition of anonymity.

Supporters of the Umma Party, Sudan's largest political party, chant slogans during a protest against a military coup that overthrew the transition to civilian rule, on 29 October, 2021

In Sudan, where organisers hope to hold a "million-strong" march against the coup, the mood was defiant.

"We will not be ruled by the military. That is the message we will convey" at the protests, said Sudanese rights activist Tahani Abbas.

"The military forces are bloody and unjust and we are anticipating what is about to happen on the streets," Abbas said. "But we are no longer afraid."

'Grave setback'

Sudan has been led since August 2019 by a civilian-military ruling council, alongside Prime Minister Abdalla Hamdok's government, as part of the now stalled transition to full civilian rule.

Hamdok himself was briefly detained before he was released and placed under effective house arrest. Other civilian leaders and ministers are still being held.

Days of unrest have rocked Khartoum and other cities.

Protesters have barricaded roads with rocks, debris and burning tyres.

Shops have largely been shuttered, and government workers have refused to work as part of a civil disobedience campaign.

"The Sudanese people are determined to... win back the gains of the December 2018 revolution" against Bashir, said Abdelgelil al-Basha from the capital's twin city of Omdurman.

Burhan, a senior general under Bashir's three decades of iron-fisted rule, has insisted the military takeover "was not a coup" but only meant to "rectify the course of the Sudanese transition".

The move triggered a wave of international condemnation and several punitive measures, with the World Bank and the United States freezing aid -- a heavy blow to a country already mired in a dire economic crisis.

US President Joe Biden has called the coup a "grave setback", while the African Union has suspended Sudan's membership for the "unconstitutional" takeover.

On Friday, UN secretary-general Antonio Guterres called on the military to show restraint as he reaffirmed his "strong condemnation" of the coup.

"People must be allowed to demonstrate peacefully," Guterres said.

Monday's military grab was the latest coup to hit impoverished Sudan, which has enjoyed only rare democratic interludes since independence in 1956 and spent decades riven by civil war.