Thirteen suspects have been charged with conspiracy to murder and murder over the death last year of Nigerian Justice Minister Bola Ige.

Eleven suspects were charged in the High Court in the south-western city of Ibadan with two more charged in absentia.

Mr Ige, a close friend of President Olusegun Obasanjo, was shot dead at his private residence in Ibadan on 23 December.

He is the most senior politician to be murdered since democratic rule returned to Nigeria in 1999.

He was also an outspoken critic of the previous military dictator, Sani Abacha, and served time in prison for his beliefs.

There was heavy security in court, reports the French news agency, AFP.

The suspects include Alani Omisore, a younger brother of Osun State Deputy Governor Iyiola Omisore, and Lambe Oyasope, a member of the Osun state legislature.

Ibadan is in Oyo State, which borders Osun.

Also among those facing charges were the justice minister's driver, two drivers from his office, and a police sergeant, AFP said.

Motive unclear

At the time of his murder, several different possible motives were advanced.

Obasanjo and Ige were close friends

Police offered a 500,000 naira reward - about 15 times the average yearly per capita income in the country - for information leading to the killers.

Before his death, Mr Ige was involved in a power-struggle in his native Osun state.

He was also a prominent opponent of the imposition of Islamic or Sharia law in the north of Nigeria and has led to an upsurge in ethnic violence.

He was also very public in his fight against drug traffickers.

Mr Ige, who was 71, was an influential figure in the ethnic Yoruba community.