An army general has been sworn in as Guinea-Bissau's new head of state a day after an apparent coup.

Gen Horta N'Tam becomes the transitional president for a period of one year. He took the oath on Thursday, in brief and muted proceedings in the army headquarters.

The military had already suspended the electoral process and blocked the release of the results of Sunday's presidential election which were expected on Thursday.

Some civil society groups in Guinea-Bissau have accused outgoing President Umaro Sissoco Embaló of masterminding a simulated coup against himself with the help of the military, saying it was a ruse to block election results from coming out in case he loses.

This manoeuvre aims to prevent the publication of the electoral results scheduled for tomorrow, November 27, the civil society coalition Popular Front said in a statement on Wednesday.

The president has not responded to the allegations. He has said he has survived multiple coup attempts during his time in office. However, his critics have previously accused him of fabricating crises in order to crack down on dissent.

Sandwiched between Senegal and Guinea, the West African country is known as a notorious drug-trafficking hub where the military has been influential since independence from Portugal in 1974.

Guinea-Bissau has witnessed at least nine coups or attempted coups over the last five decades.

The latest of these, on Wednesday, saw a group of military officers announce they have seized control of the country, following reports that President Embaló had been arrested.

Gunshots were heard in the capital, Bissau but it was not immediately clear who was involved in the shooting or if there were any casualties.

The officers then appeared on state TV, saying they had suspended the electoral process. They said they were acting to thwart a plot by unnamed politicians who had the support of a well-known drug baron to destabilise the country, and announced the closure of its borders and imposed a night-time curfew.

The election results were expected on Thursday - both Embaló and his closest rival Fernando Dias had claimed victory.

Late on Wednesday afternoon, Embaló told France 24 in a phone call: I have been deposed. Government sources later told the BBC that Dias, Pereira and Interior Minister Botché Candé had also been detained.

In a joint statement, leaders of election observation missions from the African Union and the West African bloc Ecowas expressed deep concern with the announcement of a coup d'etat by the armed forces.

Portugal, the country's former colonial ruler, has called for a return to constitutional order, with its foreign ministry urging all those involved to refrain from any act of institutional or civic violence. As of Thursday, the AFP news agency reported that Guinea-Bissau's borders had reopened.