Sudan's police Tuesday ordered its forces to avoid intervening against protesters as three Western nations threw their weight behind demonstrators' demands for a political transition plan in the country.
The call by the police, following a policy of non-intervention by the military, came as thousands of protesters massed for the fourth straight day outside army headquarters in Khartoum, urging the top brass to back their call on President Omar al-Bashir to resign.
The protests, which first began in December, pose the biggest challenge to President Bashir in his three decades of iron-fisted rule.
Thousands chanting "freedom, freedom" stayed camped outside army headquarters in Khartoum since Saturday, after security forces abandoned two separate bids to disperse them when soldiers fired in the air to protect demonstrators earlier in the day, witnesses said.
"We call on God to preserve the security and calm of our country ... and to unite the Sudanese people .. for an agreement which would support the peaceful transition of power," police spokesman said in a statement.
It added that police had "ordered all its forces" not to "intervene against the citizens or peaceful rallies".
The United States, the United Kingdom and Norway too called for a transition plan.
"The time has come for the Sudanese authorities to respond to these popular demands in a serious and credible way," the embassies of the three countries said in a joint statement.
"The Sudanese authorities must now respond and deliver a credible plan for this political transition."
Thousands have been rallying since Saturday outside the sprawling complex that also houses the President's residence in the largest demo since the protests erupted against a three-fold increase in bread prices in December.
The demonstrations have since mushroomed in towns and cities across the northeast African country, widening their demands to call for Bashir to step down.
Early on Tuesday, members of the National Intelligence and Security Service and riot police fired tear gas at the protesters in an abortive bid to end their sit-in, protest movement organisers said.
"There was heavy firing of tear gas after which army soldiers opened the gates of the compound for protesters to enter," a witness told AFP.
"A few minutes later a group of soldiers fired gunshots in the air to push back the security forces who were firing tear gas."
A second witness said soldiers had intervened against the security agents.
Since the protests erupted in December, the armed forces have remained on the sidelines even as security agents and riot police have cracked down.
On Tuesday, the crowds could be seen hoisting soldiers into the air on their shoulders, and dancing and chanting with them.
The demonstrators have called on the army to protect them from the deadly crackdown, during their four days camped outside its headquarters.
Hours later, security forces made a second attempt to clear the sit-in Tuesday, witnesses said.
They fired tear gas and shot in the air as they approached the area, witnesses said, adding that soldiers intervened again firing in the air.
Footage obtained by AFP in Paris showed security agents also firing in the air to clear the sit-in on Monday, an operation which also had to be abandoned after troops intervened.
Troops can be seen firing machine-guns as protesters run in groups, some taking shelter behind army vehicles and chanting "Allahu Akbar (God is Greatest)".
Defence Minister General Awad Ibnouf vowed the army would prevent any slide into chaos.
"Sudan's armed forces understand the reasons for the demonstrations and is not against the demands and aspirations of the citizens, but it will not allow the country to fall into chaos," Mr Ibnouf said on Monday, quoted by the official SUNA news agency.
In a separate statement, army chief of staff Kamal Abdelmarouf said the military was "discharging its responsibility in securing and protecting citizens".
Officials say 38 people have died in protest-related violence since December.
After a meeting chaired by Mr Bashir on Sunday, Sudan's security council said the demands of the protesters "have to be heard".
President Bashir -- wanted by the International Criminal Court in The Hague on charges of war crimes and genocide connected with the suppression of a now 16-year-old ethnic minority rebellion in the western region of Darfur -- took power in an Islamist-backed coup in 1989.
He has responded to the unrest with tough measures that have seen protesters, opposition leaders, activists and journalists arrested.
Interior Minister Bushara Juma said seven protesters died and 15 were wounded on Saturday while 2,496 arrests were made.
The umbrella group spearheading the protests has appealed to the army for talks on forming a transitional government.
Omar el-Digeir, a senior member of the group, said protest organisers had formed a council to open talks aimed at agreeing a "transitional government that represents the wish of the revolution".