Streets across Sudan's capital have been left empty on the first day of a general strike urged by protest leaders demanding the resignation of the ruling military council.
The Sudanese Professionals Association (SPA) called on people to stay at home, starting on Sunday, in protest at the military's deadly crackdown last week, when security forces violently dispersed the group's main sit-in outside the military headquarters in Khartoum.
The protesters say more than 100 people have been killed since the crackdown began last Monday.
The SPA spearheaded months of mass protests that led to the military overthrow of president Omar al-Bashir in April, and called on people to remain in the streets until a full handover of power to civilians.
Mr al-Bashir was overthrown after four months of mass rallies but has refused demonstrators' demands for an immediate move to civilian rule, instead pushing for a transitional power-sharing arrangement.
The SPA posted photos it said were of an empty Khartoum International Airport.
It said airport workers and pilots were taking part in the civil disobedience.
Videos circulated online showed offices and businesses closed and light traffic, in both Khartoum and the Red Sea city of Port Sudan.
Heavy deployment of troops from the paramilitary Rapid Support Forces (RSF) was reported in several parts of the capital and its sister city of Omdurman.
Security forces removed barricades from the main roads and opened the sit-in area outside the military's headquarters for the first time since the dispersal.
The SPA urged protesters to avoid clashes with the RSF.
Protesters have accused the RSF, which grew out of the notorious Janjaweed militias used by Mr al-Bashir in the Darfur conflict in the early 2000s, of leading the nationwide crackdown.
The SPA has called for the force to be disbanded.
"The peaceful resistance by civil disobedience and the general political strike is the fastest and most effective way to topple the military council... and to hand over power to a transitional civilian authority," the SPA said.
It called on international agencies to refrain from dealing with the military council.
The SPA said security forces have arrested and intimidated activists, bankers, doctors, air traffic workers and other professionals in recent days.
"Dozens of airport workers have been arrested by intelligence and the RSF since Monday.
"We do not know their whereabouts.
"New workers have been seen in the past days to replace those who took part in the strike," an airport worker said on condition of anonymity, fearing reprisal.
The state-run SUNA news agency cited authorities as saying the airport was functioning normally and that all workers had reported for duty on Sunday.
The leading opposition Umma party said that security forces had arrested one of its leaders, Adel al-Mufti, along with other opposition figures, including Mohammed Esmat, a negotiator for the protesters.
Mr Esmat was detained after meeting with the Ethiopian Prime Minister Abiy Ahmed on Friday.
Mr Ahmed met separately with the ruling generals and the protest leaders in an effort to revive talks.
A spokesperson for the military council did not immediately respond to calls seeking comment.
Pope Francis on Sunday told the faithful in St. Peter's Square that the news from Sudan is causing "pain and worry".
He prayed that violence would cease and that the common good would be sought through dialogue.