Nigeria has granted asylum to Guinea-Bissau presidential candidate Fernando Dias da Costa just days after a coup prevented the results of the recent election being announced.

The 47-year-old, who ran as a candidate for the Party for Social Renewal, was under special protection at the Nigerian embassy, following "threats made against" him, Nigeria's foreign minister said.

Dias was the main challenger to Umaro Sissoco Embaló, who was seeking a second term as president and has left the country following the military takeover.

A delegation from the West African bloc Ecowas has been in the country, urging the military to step aside and release the results of the vote.

Both Embaló and Dias had claimed victory in presidential poll held on 23 November.

The PAIGC party, the liberation movement that ended Portuguese colonial rule, had been barred from fielding a candidate.

The coup took place three days after the vote. The military suspended the electoral process, blocked the release of the results and insisted it was acting to thwart a plot to destabilise the politically unstable country.

The junta has also tightened restrictions in the country, banning all demonstrations and "all disturbing actions of peace and stability in the country". 

Tensions remain high in the capital, Bissau. PAIGC said its headquarters had been "illegally invaded by heavily armed militia groups" following the coup.

Its leader, Domingos Pereira, was arrested on the day of the coup, according to family and party members.

Dias said he escaped from his campaign headquarters on the day of the coup as armed men came to arrest him.

Nigeria's Foreign Minister Yusuf Tuggar said President Bola Tinubu had agreed to give Dias protection inside the Nigerian embassy in Bissau.

"The decision to accommodate Mr [Fernando Dias] da Costa in the Nigerian premises underscores our firm commitment to safeguarding the democratic aspirations and the sovereign will of the good people of Guinea-Bissau," Tuggar said in a letter to Ecowas Commission president Alieu Omar Touray.

The letter also asked that soldiers from an Ecowas unit in the country be deployed to the Nigerian embassy to keep Dias safe.

Meditation talks on Monday between the Ecowas delegation, led by Sierra Leone's Foreign Minister Alhaji Musa Timothy Kabba, and the junta were heated.

Afterwards, Kabba told journalists that the discussions were "productive," but noted that "both parties expressed their concerns". 

The junta has already sworn in a new transitional leader, Gen Horta N'Tam, who will rule the country for a year.

Ecowas leaders have suspended Guinea-Bissau from all decision-making bodies until constitutional order is restored.

The true motives behind the coup in Guinea-Bissau remain unclear amid speculation that it may have been staged.

Senegal's Prime Minister Ousmane Sonko and Nigeria's ex-leader Goodluck Jonathan have both said the coup was fabricated without providing evidence. 

Some local civil society groups have also accused 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 lost.

Embaló, who has previously faced accusations of using crises to quash dissent, has not responded to the coup allegations.

The 53-year-old was allowed to leave for neighbouring Senegal on Thursday, from where he reportedly moved on to Congo-Brazzaville at the weekend.

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

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