One day after the death of Guinea-Bissau's president Malam Bacai Sanha, opposition parties are rejecting a plan for the head of the National Assembly to serve as interim president.

Under the constitution, the parliament chief is to serve as interim leader and organize elections, which are to be held within 90 days of the president's death.

But on Tuesday, a coalition of opposition parties released a statement rejecting National Assembly leader Raimundo Pereira as interim president. The parties questioned whether Pereira would faithfully carry out the constitution.

Mr. Sanha's death has raised concerns of a power struggle in the small West African country, known for its history of political instability and unrest.

The head of the Economic Community of West African States has called for a smooth, constitutional transition of power in the country.

In an interview with VOA , ECOWAS chief James Gbagho said the bloc would keep developments in Guinea-Bissau “under close watch.”

Late last month, dozens of military personnel were arrested after a suspected coup attempt. Those arrested include the country's navy chief, Bubo Na Tchuto, who was accused of masterminding the plot.

The late Mr. Sanha was elected to replace President Joao Bernardo Vieira, who was killed by mutinous soldiers in March 2009.

Mr. Sanha died Monday in a Paris hospital, where he was undergoing treatment for an undisclosed condition. The 64-year-old leader was known to have had diabetes and a blood ailment and had been hospitalized repeatedly since becoming president.