Street protesters in Sudan pressing for a change of leader and regime achieved a remarkable turnaround last week – but not the sort they were hoping for.

President Omar al-Bashir, who seized power in a coup 30 years ago and has clung on tenaciously since, unexpectedly stood down as head of the ruling National Congress party (NCP). But rather than open the door to reform, as protesters demanded, Bashir gave power to a close ally – who, like him, has been charged by the international criminal court (ICC) with war crimes in Darfur.

Ahmad Harun, former governor of North Kordofan state, would serve as acting party leader, an NCP statement said. Harun was appointed deputy leader last week, after Bashir declared a state of emergency.

The move by Bashir – who remains president – may have been tactical, analysts say, designed to defuse tensions within the ruling party between its Islamist wing and senior military figures representing the security establishment.

Perhaps he had no choice. The state of emergency declaration, Bashir’s simultaneous dismissal of his government, and his replacement of all 18 state governors with loyalists, could have been necessitated by a threatened internal party putsch, the International Crisis Group (ICG) thinktank suggested.

“Leaders [of the Islamist wing] are said to advocate a more positive response to demonstrators’ demands. If the split deepens, it could raise the spectre of a dangerous confrontation between these well-organised and well-armed camps,” the ICG said.

It is also possible Bashir’s decision to step back marks the beginning of the end for one of Africa’s longest-serving leaders. Like Algeria’s 81-year-old president, Abdelaziz Bouteflika – also the target of big weekend demonstrations – Bashir, 75, is a long-time fixture who seems to have outstayed his welcome.

Bashir has battled international ostracism and western sanctions since being accused by the ICC of overseeing a genocide in Darfur in the early 2000s that killed an estimated 300,000 people. In a Guardian interview in his Khartoum palace in 2011, he denied the charges.

The decades-long war that ended with South Sudan’s independence in 2011 also weakened Bashir’s leadership and deprived Khartoum of vital oil revenues. NCP mismanagement and corruption have helped bring Sudan’s economy to its knees.

New generations of Sudanese, including doctors, engineers and younger party members frustrated by multiple governance failures, have plainly run out of patience, as have impoverished urban workers. Hence the persistent anti-Bashir protests in many town and cities, the biggest since 2013.

The latest round of demonstrations began in December, sparked by a sharp rise in the price of bread. But unrest quickly took on a political complexion, with demands for Bashir’s resignation and an end to NCP hegemony.

Despite vicious and uncoordinated attempts by the security forces to halt the protests – Human Rights Watch says more than 50 people have died – and a half-hearted offer of dialogue by Bashir, demonstrations continued at the weekend. So far, however, the protesters lack leaders or clear objectives, let alone a plan for a post-Bashir era.

Opposition is focused, in part, on proposed constitutional changes that would allow Bashir to stand for re-election in 2020. These have now been deferred. But Bashir could yet run again – if he obtains NCP backing – and has meanwhile placed the entire country under de facto martial law.

As in 2011, when emergencies were declared in several provinces to quell unrest, this entails additional army deployments, roadblocks to control civilian population movement, arbitrary arrests and seizures, media censorship and bans on anti-regime political groups. Security forces can and do act with impunity.

“The risk of an escalation of violence is higher now than it has been at any time since protests broke out,” the ICG warned. “With the regime’s back to the wall, [security] forces are likely to behave with even greater brutality.”

It is unlikely the promotion of Harun, who may hope to become Bashir’s heir apparent, will bring radical change. Like his mentor, he holds uncompromising views on the challenges facing the country.

Interviewed in 2008, Harun said he was innocent of crimes committed in Darfur when he was a minister of state. He claimed the allegations and Sudan’s problems were the product of an international conspiracy, and the ICC was an integral part of it.

“It is another phase of international colonisation. It targets mainly the Africans,” he said. “The main aim of the white people in Africa at that time, the British and the Europeans, was to disseminate their culture and their traditions … Now there is a new imperial era, but this time it is led by the United States and supported by the Europeans.”

Harun’s suspicious outlook, shared by many in Sudan, underscores the difficulties western countries face in trying to induce Bashir to halt the violence, allow a transitional government of national unity and, perhaps, bow out peacefully.

That responsibility may fall to Sudan’s African partners, and Middle Eastern allies such as Saudi Arabia, the UAE, Qatar and Turkey. So far there is no sign they will intervene.