Six of the nine Catalan separatist leaders in custody over their role in Catalonias secession bid were transferred Wednesday to prisons in the region as part of Madrids efforts to ease tensions ahead of talks next week.

Four were moved to a prison in Lledoners, some 70 kilometres (45 miles) north of Barcelona, a spokesman for Catalonia's regional justice authorities told AFP.

These are former Catalan vice president Oriol Junqueras, Jordi Sanchez and Jordi Cuixart of two pro-independence associations and Raul Romeva, the former Catalan government's international affairs chief.

Another two prisoners -- Carme Forcadell, former regional parliamentary speaker, and Dolors Bassa, who held the labour portfolio in the former government -- were transferred later Wednesday to a prison near Figueras, 140 km northeast of Barcelona.

The last three imprisoned former leaders will be transferred to Catalonia next week, the regional justice spokesman added.

Accused of rebellion along with deposed Catalan leader Carles Puigdemont for their role in the region's proclamation of independence in October 2017, they face up to 25 years in jail.

Spain's Socialist Prime Minister Pedro Sanchez has been in power for a month after overthrowing his conservative predecessor Mariano Rajoy.

Last week he urged Catalan separatist leaders to "turn the page" on the contested independence referendum after regional president Quim Torra said he wanted another vote.

The transfers come before a July 9 meeting in Madrid between Sanchez and Torra.

Spain's right-wing opposition has criticised the prisoner transfer, accusing the Sanchez government of going soft on the separatists.

"They are nearer to us now, but they are not where they should be, in the street," Torra said

But the separatists and their supporters demand the men's release, saying they are "political prisoners".

Protests were expected later Wednesday outside the two prisons.

"They are nearer to us now, but they are not where they should be, in the street," Torra, who will be visiting the prisoners in Lledoners, said.

Puigdemont is in Germany where he is awaiting possible extradition after going into self-imposed exile.