Nigerian security forces blocked traffic and tightly controlled access to an Abuja courthouse where the trial of a separatist leader was due to resume on Monday, Reuters witnesses said.

Nnamdi Kanu, leader of the Indigenous People of Biafra (IPOB), a banned organisation campaigning for secession in southeast Nigeria, was due to appear at the Federal High Court to face 11 charges including treason.

The case is one of two on Monday in which Nigerian authorities are seeking to prosecute citizens campaigning for autonomy in different regions of Africa's most populous nation.

The cases underline the government's concern over growing discontent and insecurity in various regions of Nigeria.

In Cotonou, Benin, Nigerian authorities are seeking the extradition of Sunday Adeyemo, known locally as Sunday Igboho, a Yoruba activist it accuses of plotting a violent insurrection in the southwest of the country. Security forces raided his compound in Ibadan on July 1, claiming they found a stockpile of weapons there.

Kanu was first arrested in 2015, but disappeared while on bail in April 2017 after two years in jail fighting charges. His social media posts during his absence outraged the government, which said they sparked some attacks on security forces in southeastern Nigeria.

His whereabouts were unclear until security agents produced him in an court in Abuja on June 29, saying that he had been detained abroad, but not where. His lawyer alleged he was detained and mistreated in Kenya, though Kenya has denied involvement.

IPOB wants a swathe of the southeast, homeland of the Igbo ethnic group, to split from Nigeria. An attempt to secede in 1967 as the Republic of Biafra triggered a three-year civil war in which more than a million died, mostly from starvation.