Mr Conté declared martial law late on Monday following renewed outbreaks of violence across the West African country and the resumption of a general strike by unions demanding the former military officer stand down.

Diplomats in the region said that by effectively handing power to the army, Mr Conté may have succeeded in persuading top military leaders to back him for now. But they warned that the embattled and ailing president had also narrowed the window for political dialogue that might lead to a resolution to the crisis.

The president was apparently shaken, they said, by news that soldiers rioted at a key army barracks in the capital, Conakry, on Monday, complaining they were not as well paid as the presidential guard, which includes some foreign soldiers. Mr Conté, who took power in 1984, was himself almost toppled in a military mutiny in 1996.

The army moved quickly on Tuesday to re-establish order, clamping down in Conakry and other towns and imposing a 20-hour-a-day curfew while sporadic violent protests continued. Scores of protesters have been killed in recent weeks.

But union and opposition leaders have refused to be bowed and continue to call for Mr Conté to step down, saying he is to blame for declining living standards. The imposition of martial law, which is set to last at least 11 days, will however curtail protest and force union leaders to consider their options.

Diplomats fear that a prolonged political conflict that sets Guinea’s military, which is itself divided along generational and ethnic lines, against an angry and hungry general population could have dangerous repercussions in a region awash with small arms.

Guinea has been intricately linked to the wars that took place from the 1990s in Sierra Leone and Liberia, neighbouring countries where billions of dollars have been spent on peacekeeping missions. Partly as a result, the rule of Mr Conté in the former French colony, rich in mineral reserves, has been relatively unquestioned.

Victor Angelo, the most senior United Nations official in Sierra Leone, warns that if a political solution cannot be found to calm tensions in Guinea “it will have significant consequences in the peace consolidation processes Sierra Leone and Liberia are now implementing”.

Both countries are recovering from devastating civil wars and need Guinea, which as well as providing peacekeepers had also helped Liberia and Sierra Leone by taking in hundreds of thousands of refugees, to remain stable.

UN investigators have said they believe many weapons were returned to Guinea after the Liberian war by former Liberian rebels who launched their rebellion from Guinea. Sierra Leone, which saw its large UN peacekeeping mission draw down early last year, has also had problems with Guinean military encroaching into its territory.

Diplomatic efforts to resolve the crisis have run aground, with Mr Conté rejecting early efforts at mediation by Ecowas, a west African regional grouping that would be the first line of international diplomacy with Guinea. Mohammed Ibn Chambas, Ecowas executive-secretary, said that the grouping was sending in a new diplomatic delegation to prepare the ground for more extensive talks later this week.

But he criticised Mr Conté for responding to union demands for the appointment of a new prime minister with sweeping powers by filling the post with a close political ally.