Guinea-Bissau military officials have denied the army was involved in the assassination of an ex-intelligence chief in a country where murder often settles scores between the military and the state.

Daba Na Wagna, co-ordinator of a joint military-police election security team said Colonel Samba Diallo's murder Sunday night was "deplorable because there was a loss of human life, but the army was not involved from any angle."

Na Wagna was speaking after a meeting between the national elections commission and army chief Antonio Indjai in which it was decided to boost security around elections officials and locations.

Diallo was shot dead by men in military dress as he sat on the terrace of a restaurant near his home, sources said.

He was director of military intelligence until April 2010, when he was arrested with other top officers on suspicion of involvement in a 2009 bombing that killed the country's then army chief and prompted the murder of president Joao Bernardo Vieira in a revenge attack a few hours later.

No clear motive has emerged for Diallo's killing killing, which came as votes were being counted in a presidential election.

The incident raised fears that a military dispute may again derail the political process in a country which sorely needs stability to push forward with development.