Police in Ghana said on Wednesday they had arrested 81 people accused of supporting the declaration of an eastern region as an independent country.
The sweeping arrests follow the detention of eight of the group's reported leaders on Sunday as they prepared to declare the region as their own nation, according to officers, meaning a total of 89 have been detained.
Police said the group were members of the "Homeland Study Group Foundation", or HGSF, which campaigns for a separate nation in Ghana's eastern Volta region, which they call "Western Togoland".
The arrests on Wednesday were made in a joint military and police operation across the Volta region, the majority around the town of Ho, some 150 kilometres (95 miles) northeast of the capital Accra.
"We arrested 81 members of the Homeland Study Group Foundation for their involvement in an intended demonstration against the arrest of their leaders," said Prince Dogbatse, police spokesman of the Volta region.
Of the 81 arrested, two of them are women.
The HGSF group, which formed in 1994, says it works to advance the rights of the people in eastern Ghana.
"The suspects were picked up after a tip-off by joint police and military forces at various entry points to the Volta region," Dogbatse added. "We are going to process them for court this week."
Those arrested on Sunday included the group's leader, 85-year-old Charles Kormi Kudjordji.
Kudjordji was released on bail on Wednesday due to his age, but the rest were remanded in custody.
They face potential charges of conspiracy to commit treason, as well as charges connected to the alleged training of a militia force.
In 2017, HGSF leaders were arrested and warned not to engage in activities against the state.
Multiple ethnicities live in the region, a place with a history of rule by three colonial European powers.
Britain seized much of what is today Ghana, and Germany grabbed neighbouring Togo.
After Germany's defeat in World War One, the land was split between British Togoland and French Togoland.
When Britain left its empire in Africa, British Togoland became part of eastern Ghana in 1956.
But separatists say the area has its own unique history and culture, and want a country of their own.