Diplomats said it was not clear if the struggle would produce a clear victor or further muddy the turbulent politics of Africa's biggest country, riven by a 16-year-old civil war.

``If Bashir wins, it could lead to more stability as the regime will then speak with one voice,'' said an African diplomat. ``If the dust settles, it could be very positive.''

Troops sealed Sudan's parliament building and guarded key points around Khartoum on Monday, hours after Bashir declared a three-month state of emergency and dissolved parliament.

A rift had been widening between the two top men in the Islamist-led government, battling a shaky alliance of southern rebels and northern-based Moslem parties.

The war, which broadly pits the mainly animist and Christian south against the Moslem-dominated north, has cost an estimated 1.5 million lives in fighting and war-related famine.

One opposition figure saw the Bashir-Turabi quarrel as heralding the demise of their decade-old attempt to turn religiously-mixed Sudan into a purist Islamic state.

``This is the beginning of the end of the NIF (National Islamic Front) project, as a whole, including Bashir, based on fundamentalism,'' said Farouq Abu Eissa, spokesman for the National Democratic Alliance (NDA).

``It is natural, because any dictatorial regime destroys itself. The cracks started to appear a while ago,'' he said.

Sudanese opposition parties have confidently predicted the government's downfall for years, but it has stubbornly pursued the war with rebels and withstood U.S. hostility that culminated in the 1998 bombing of a Khartoum medicine factory.

The start of oil exports this year boosted government hopes of reviving an economy debilitated by war and mismanagement.

REPAIRING TARNISHED REPUTATION

In recent years, Khartoum has tried to polish its image, passing a 1998 constitution ostensibly aimed at restoring multi-party democracy, inviting banned opposition leaders to return home and patching up strained ties with its neighbours.

The government, accused by the West of sponsoring terrorism, has been slowly emerging from diplomatic isolation.

This year Bashir struck reconciliation agreements with Eritrea and Ethiopia. Last week he signed a peace deal with Uganda under which both sides are to end their support for rebel armies fighting in each other's countries.

Bashir had been expected to visit Cairo this month to seal an improvement in relations that have been strained since Egypt accused Khartoum of sheltering Moslem militants who tried to kill President Hosni Mubarak in Addis Ababa in 1995.

These efforts could go to waste if the Bashir-Turabi rivalry turns bloody. Both leaders have guns at their disposal.

A European diplomat said the president, a lieutenant-general, might command the allegiance of the army rank and file, but Turabi had placed many of his loyalists in senior positions in the military and security forces.

Bashir, by acting first, appeared to have gained control of the capital unopposed and the mood on the street seemed to be running in his favour, residents said.

``It was long overdue. The general population is fed up with Turabi,'' said the African diplomat based in Cairo.

ACCUSATIONS FLY

Bashir said he had acted to ``restore discipline and order'' after failing to resolve his dispute with the ruling National Congress Party dominated by Turabi, its secretary-general.

Turabi decried the ``coup d'etat'' by his one-time comrade, who installed Islamist rule after his 1989 military coup.

The crafty Islamic ideologue denounced Bashir's action as a betrayal of his party and a violation of the constitution.

``We will take the case to the grass roots of the National Congress and decide what to do. If these political measures fail, popular forces will have to do something,'' Turabi added.

Both Bashir and Turabi had been involved in a drive to build bridges to opposition parties and to persuade them to take part in a national reconciliation conference.

Bashir and the man he toppled as prime minister in 1989, Sadeq al-Mahdi of the northern-based Umma Party, met in Djibouti on November 26 and agreed to hold talks on how to promote democracy and end the war. Turabi had met Mahdi in May.

The African diplomat said it was not inconceivable that Bashir would turn to Mahdi as a new ally in place of Turabi.

``Mahdi might come rushing back as prime minister, though this might be a miscalculation for Bashir as Mahdi is not so popular. Many people see him as part of the problem,'' he said.