Portugal has sent a team of investigators and police experts to São Tomé and Príncipe following an "urgent request for assistance" in the wake of an alleged coup attempt that left four people dead, the authorities of both countries have said.

The team was sent on Sunday and will "work directly with the judicial authorities" to investigate the events that took place last Thursday and Friday night.

Four people were arrested and later died, according to the army chief of staff, who gave no further details about the circumstances, which remain unclear.

The São Toméan government said it "strongly condemned" what it described as a "violent attempt to subvert the constitutional order", while assuring that "all investigations will be carried out to determine the causes and circumstances of the deaths", in addition to the investigations to determine who was responsible for the coup attempt.

What is known about this alleged Coup attempt?

Prime Minister Patrice Trovoada announced on Friday that the security forces had killed four people and arrested two others, including politician Delfim Neves, following an attempted coup d'état.

Trovoada said the authorities believe the men were looking for weapons when they entered the military barracks and kidnapped a hostage, who was later released.

Authorities were investigating whether the men received any support from the military, he added.

"It's not a robbery, it's not a theft," said Trovoada. "It's an attack with weapons of war on the country's armed forces and we have to solve this problem."

The attack comes about two months after legislative elections were held in São Tomé and Príncipe, which were won by Trovoada's Independent Democratic Action (ADI) party.

Trovoada took office as prime minister earlier this month.

Neves, of the Democratic Convergence Party, has run for president twice and had contested the results of last year's race.

The archipelago of São Tomé and Príncipe is located near the equator, about 350 kilometers off the west coast of Africa, close to Gabon.

Around 225,000 people live in the archipelago, which has seen several coup attempts, including in 2003 and 2009. But since then the island nation has been considered a model of parliamentary democracy in Africa.

The government has alternated several times between the two main parties: the center-left Movement for the Liberation of São Tomé and Príncipe - Social Democratic Party; and Trovoada's center-right Independent Democratic Action (ADI). (Euronews)