Four former army officers have been condemned to death by a military tribunal in Equatorial Guinea for their involvement in an attack on the presidential palace in 2009, state television reported Sunday. A human rights campaigner tells RFI that they were executed before sentence was officially passed.

The four, who include a member of the presidential guard and two army captains, were sentenced on Saturday. They were found to have been "criminally responsible" for an attempt on the life of head of state, President Teodoro Obiang Nguema, as well as being guilty of terrorism and treason.

The condemned men had already been executed before the trial, according to Tutu Alicante, the US-based president of the NGO EG justice.

"I have spoken to sources from inside the country who have confirmed that these four individuals [...] have all been already executed," he told RFI "This sentence was handed down supposedly yesterday but it appears that these four men were actually killed on Friday."

Two other men were condemned to 20 years in prison for complicity.

The attack took place in February 2009, when armed men arrived in a boat and tried to land but, according to the authorities, were beaten off. The motive for the assault remains mysterious.

Officials first blamed the Nigerian rebel group, Mend, and then accused former opposition party leader Faustino Ondo Ebang of ordering the attack. Ebang fled to Spain.

The Security Minister at the time, General Manuel Nguema Mba, was sacked along with four generals and other officials, but named presidential advisor on security in March this year.