Sudanese protesters have been forced to block an apparent attempt to break up their sit-in outside the defence ministry in Khartoum, where demonstrators have been pushing for a quick transition to civilian rule after Omar al-Bashir was ousted as president.

Protesters said they had joined hands and formed a ring around the sit-in area on Monday after troops gathered on three sides and tractors were preparing to remove stone and metal barricades.

Clips posted on social media showed a lengthy standoff as several thousand protesters chanted “freedom, freedom” and “revolution, revolution”, and appealed to the army to protect them.

Earlier, the Sudanese Professionals Association (SPA) protest group issued an urgent call for people to join the sit-in and block any attempt to disperse it. “We hope that everyone will head immediately to the areas of the sit-in to protect your revolution and your accomplishments,” the SPA said.

The confrontation came as a series of representatives of western countries, including the UK and US, had their first meetings with Sudan’s new rulers, while the African Union issued a statement calling for the army to give way to a civilian government within two weeks.

The sit-in outside the compound, which also includes the intelligence headquarters and the presidential residence, began on 6 April after more than three months of protests triggered by a deepening economic crisis.

On Thursday, Sudan’s army announced it had removed and detained Bashir after three decades in power and was setting up a transitional military council to run the country.

Since then the heads of the council and Sudan’s powerful intelligence services have both been replaced, as protesters have continued to call for change. The SPA has demanded the immediate handover of power to a civilian transitional government and the prosecution of former officials.

The military council met political parties on Sunday and urged them to agree on an “independent figure” to be prime minister, an AFP correspondent at the meeting said. “We want to set up a civilian state based on freedom, justice and democracy,” one council member, Lt Gen Yasser al-Ata, told members of several political parties.

A 10-member delegation representing the protesters delivered a list of demands during talks with the council late on Saturday, according to a statement by the Alliance for Freedom and Change umbrella group. But in a press conference the council’s spokesman did not respond to the protesters’ latest demands.

Protesters in Khartoum. Photograph: Ebrahim Hamid/AFP/Getty Images

The western diplomats angered some protesters by meeting Gen Mohammad Hamdan Daglo, the deputy chief of the military council. Widely known as Himeidti, he heads the feared Rapid Support Force (RSF) that grew out of the “Janjaweed” militia accused of abuses in Darfur.

The British ambassador tweeted that he had met with Daglo “not to endorse or confer legitimacy … but to stress steps UK wants to see taken to improve situation in Sudan.”

Irfan Siddiq said he had made clear there should be “no violence and no attempt to forcibly break the sit-in”, a swift formation of a civilian transitional government through a transparent, credible and inclusive process, and clarity on the whereabouts of Bashir and other former senior regime figures.

“Transparency builds confidence. Finally, expressed concerns about historic role of RSF. Allegations of abuses and crimes need to be addressed to build confidence,” Siddiq wrote.

Washington’s chargé d’affaires in Khartoum, Steven Koutsis, met Daglo on Sunday.

The African Union of countries has taken a harder line, condemning the “unconstitutional” military takeover and threatening to suspend Sudan from the organisation if civilian rule is not restored within 15 days.

Many regional powers are nervous of instability in Sudan causing further problems in an already volatile region.