By Loucoumane Coulibaly

ABIDJAN (Reuters) - A top military commander under Ivory Coast's former president Laurent Gbagbo was sentenced to 15 years in prison on Thursday in the first trial involving an accused instigator of last year's post-election violence.

General Bruno Dogbo Ble headed the elite Republican Guard during the brief conflict, which killed more than 3,000 people and erupted after Gbagbo refused to accept his defeat to rival Alassane Ouattara in an election held in late 2010.

"Dogbo Ble is guilty of complicity in kidnapping, illegal detention and murder ... The tribunal condemns him to 15 years of military detention," lead judge Mathurin Yao Kanga told a court in the commercial capital Abidjan.

The prosecution had requested a sentence of 20 years.

A staunch Gbagbo loyalist, Dogno Ble and four co-defendants were charged over the abduction and killing of retired Colonel-Major Adama Dosso in March 2011, at the height of the violence.

Dosso was leaving Ouattara's headquarters at Abidjan's lagoon-side Golf Hotel when he was stopped at a roadblock manned by pro-Gbagbo soldiers. It was widely believed he was planning to throw his allegiance behind Ouattara.

His body was later discovered beside a motorway.

While several of his co-defendants admitted to their role in the killing during the trial, Dogbo Ble denied ordering the murder and told the court he was proud of his service during the conflict.

The four other men, all of them soldiers, were convicted and given sentences ranging from five to 15 years.

A lawyer representing Dosso's family at the trial said they were satisfied with the decision, but Dogbo Ble's defense team said they planned to appeal the verdict.

"We raised objections that were not respected ... We're going to appeal," Mathurin Dirabou said.

Gbagbo was captured by fighters backing Ouattara during the final battle for Abidjan and is awaiting trial before the International Criminal Court on crimes against humanity charges for his alleged role in the violence.

Most of his political and military allies are either in detention in Ivory Coast or living in exile in neighboring West African nations.

United Nations investigators have accused key members of the Gbagbo regime of establishing a base in neighboring Ghana from which they are working to destabilize the current Ivorian government, according to a report seen by Reuters this week.

(Writing by Joe Bavier; Editing by Michael Roddy)