A shoot-out outside the house of a former Central African Republic ruler was an attempt to kill Andre Kolingba, his spokesman says.
Kolingba ruled CAR for 12 years
One soldier was wounded in the clash on Tuesday, announced the interior minister, who said the clash was a "misunderstanding" between soldiers.
Gen Kolingba is one of five candidates who earlier called for this month's presidential elections to be annulled.
Francois Bozize, who staged a 2003 coup, is favourite to win the poll.
"General Kolingba's residence was attacked by unidentified gunmen. We believe that there was a deliberate intention to assassinate the general," said Gen Kolingba's spokesman Gaston King Mahoutou.
He seized power in a coup and ruled for 12 years before losing elections he organised in 1993.
Most observers have given the 13 March parliamentary and presidential polls a clean bill of health but on Tuesday Union of Active Forces of the Nation (UFVN) leader Joseph Douacle cried foul.
"Given the extent of irregularities and fraud we have seen, we have no choice but to request that the vote be declared null," he said, on behalf of Gen Kolingba and four other candidates.
With 56% of the votes counted, Mr Bozize has a commanding lead.
Just 22 polling agents are counting the votes by hand but officials said the results of the elections should be released this week.
Second-placed candidate Martin Ziguele was not one of the five who complained of fraud, saying "the polling went on well".
Mr Bozize's coup was condemned internationally when he ousted the unpopular Ange-Felix Patasse, but he has gradually gained approval at home.
"A true democracy is being established. I've contributed a lot to this, and I can be proud," he said.
As well as choosing from 11 presidential candidates, voters were asked to select a new 105-seat national assembly.
The CAR has a history of coups and army mutinies, as well as endemic corruption, and remains one of Africa's least developed nations.