Unidentified gunmen have killed a presidential candidate in Guinea Bissau.  Campaigning is due to start Saturday for an election to replace long-time president Joao Bernardo Vieira who was assassinated in March.

State radio says gunmen broke into the home of Baciro Dabo around 4:00 a.m. (local) Friday morning and shot him in his bed.

The former interior minister had  close ties to President Vieira. Though he was running in this election as an independent candidate, analysts say Dabo had the backing of Prime Minister Carlos Gomes Jr.

The prime minister initially wanted the ruling party to make interim leader Raimundo Pereira its presidential candidate. But when the central committee chose former national assembly chair Malam Bacai Sanha instead, analysts say Gomes began supporting Dabo.

His murder comes just a day before the start of campaigning to replace President Vieira, who was killed in his home in March hours after a bomb blast killed his chief political rival, Army Chief of Staff General Batista Tagme Na Waie.

It is the latest violent change of power in a country that has seen a series of army mutinies and coups since independence from Portugal in 1974.

Regional diplomats say that instability has been made worse by Latin American drug gangs  using remote airstrips along Guinea-Bissau's coastline to smuggle cocaine to Europe.

Several candidates are running to succeed President Vieira. But the vote scheduled for June 28 is expected to be primarily a race between the ruling party's Sanha and the main opposition Social Renewal Party's Kumba Yala.