An international rights group has demanded Sudan's military rulers guarantee the safety of protesters ahead of planned mass rallies and following a deadly military crackdown that has left more than 100 people dead since early June.
Nationwide protests have been planned for Sunday to mark 30 years since former longtime autocratic President Omar al-Bashir took power in a military coup.
Sudan's protest leaders said they would proceed with demonstrations despite intensified efforts by the African Union (AU) and Ethiopia to end a political impasse and bring pro-democracy demonstrators and the ruling Transitional Military Council (TMC) back to the negotiating table.
The protests are planned across the country, including the capital, Khartoum.
In a statement on Friday, Amnesty International's Secretary-General Kumi Naidoosaid: "The horrific unprovoked use of lethal and unnecessary force against peaceful protesters as witnessed on 3 June must not be repeated this Sunday, or ever again."
Al-Bashir was deposed by the military in April after months of massive nationwide protests, including a sit-in outside the army headquarters in the capital, Khartoum, which continued for weeks after al-Bashir's removal as demonstrators demanded the military transfer power to civilians.
Yet on June 3, a day after talks over the make-up of a transitional government collapsed, armed men in military fatigues stormed the camp in an operation that left 120 people dead, according to a doctors group linked to the protest movement.
The health ministry said 61 people were killed nationwide on June 3.
Naidoo said that since the crackdown on the protest sit-in site, "there has been an alarming regression on human rights."
"This includes an ongoing internet shutdown, attacks on the media and the refusal to allow opposition groups to organise public forums, as well as the continued dispersal of peaceful protesters using unnecessary and excessive force," Naidoo said.
"This clampdown clearly points to the return of the repressive days associated with al-Bashir."
Negotiations between protesters and Sudan's military rulers have made little progress since the crackdown on the sit-in.
On Thursday, the Sudanese protest movement said it received a new proposal for a transition drafted by Ethiopia and the AU.
The proposal, however, fails to mention the make-up of a new transitional parliament.
"The Alliance for Freedom and Change received the draft ... and will be considering the proposal to make a decision," the umbrella group said in a statement on Thursday.