A Canadian Roman Catholic monk has been killed as forces loyal to self-declared President Marc Ravalomanana try to seize control of Madagascar's third town, Fianarantsoa.
Troops backing the town's incumbent governor in his hill-top residence exchanged fire with the attackers.
Mr Ravalomanana says he won last December's elections outright but official results say that neither he nor incumbent President Didier Ratsiraka gained the 50% of the vote needed to be declared the winner.
The country is deeply divided with rival governments, two capitals and splits in the armed forces.
Supporters of Mr Ratsiraka based in the port city of Tamatave have imposed an economic blockade on the capital, Antananarivo, which is controlled by Mr Ravalomanana.
This has led to shortages of fuel and essential commodities in Antananarivo.
'Well-armed'
The monk was hit by a stray bullet as he lent out of the window of his mission, next to the gendarmerie, AFP quotes a local journalist as saying.
The fighting in Fianarantsoa had earlier left two soldiers and a child injured, said medical sources.
Governor Emilson ignored a deadline for leaving his residence.
"We are well-protected and well-armed and have one month of supplies," one of his bodyguards told the Associated Press news agency by mobile telephone.
"About 100 members of the joint forces have begun the operation to dislodge those holding the governor's office," said Mr Ravalomanana's "interior minister", Jean-Seth Rambeloalijaona.
Correspondents say that Mr Ravalomanana's supporters believe that taking control of Fianarantsoa would enable them to lift the blockade on Antananarivo.
'Terrorists'
The conflict between Madagascar's two rival presidents has turned increasingly violent in recent days.
Earlier this week, an aide to Mr Ratsiraka died after being taken into custody by security forces loyal to Mr Ravalomanana.
On Monday, one person was killed and several others wounded during a shooting incident in Antananarivo between supporters of Mr Ravalomanana and troops loyal to Mr Ratsiraka.
The shooting occurred outside the home of Gerard Andrialemirovason, a senior aide to President Ratsiraka.
Last Friday, Mr Ravalomanana called on his supporters to hunt down his "terrorist enemies".
At the start of last week, a similar bloody attempt by supporters of Mr Ravalomanana to take over the governor's residence in Fianarantsoa failed.
At least one soldier loyal to Mr Ratsiraka was killed.