* Election a test for fragile state and region
* Three front-runners among 11 contenders
* Second round might be needed
By Alberto Dabo
BISSAU, June 28 (Reuters) - Guinea-Bissau holds an election on Sunday to replace the slain president of the West African state, which has been weakened by military rivalries, ethnic divisions and drug gangs.
President Joao Bernardo Vieira was shot dead by soldiers in March in apparent revenge for the killing of the head of the army. Eleven candidates are standing on Sunday. One top contender was killed during the election campaign.
"It’s time to end impunity, restore the state’s authority and give new impetus to the rule of law," said 40-year-old businessman Guilherme Joao da Silva in the capital Bissau, a coastal city of crumbling Portuguese colonial buildings.
The vote is a test not only for the country of around 1.6 million people, but for a region worried at the retreat of democracy after coups in Guinea and Mauritania and a deepening political crisis in Niger.
"The real test for Guinea-Bissau is not whether the election is held peacefully, but whether state institutions have the capacity to prevent the country from sliding into chaos in the aftermath," said Kissy Agyeman-Togobo of IHS Global Insight.
"The military has been far too dominant in Bissau-Guinean politics to date, so there is a real need for the international community to offer support for capacity building."
The three front-runners all pledge peace and justice.
The biggest party in parliament, the PAIGC, is represented by Malam Bacai Sanha, interim president from 1999-2000 after a coup and brief civil war.
Former President Koumba Yala, overthrown in a 2003 coup, is also expected to do well. The former philosophy professor has the backing of the biggest tribe, the Balante.
Henrique Pereira Rosa, standing as an independent, served as interim president between the overthrow of Yalla and the 2005 election won by Vieira.
It is possible there will be no outright winner in the ballot of around 600,000 voters on Sunday, meaning a second round would be held. Polling stations open at 7 a.m. (0700 GMT) and close at 5 p.m.
Guinea-Bissau’s instability and the squabbling within the military has been worsened by the involvement of Colombian cocaine cartels. They took advantage of unpoliced islands and creeks as staging points for shipping drugs to Europe.
But the U.N. body responsible for fighting drugs and crime told Reuters this week that the disappearance of many of those in Guinea-Bissau who were closest to the drug dealers had cut trafficking dramatically. [ID:nLP915688]
Guinea-Bissau’s most important formal exports are fish and cashew nuts, eaten as bar snacks or used in Asian cooking.