At least 10 soldiers loyal to Ivory Coast's disputed President Laurent Gbagbo have been killed by unidentified gunmen in Abidjan.
The army vehicles were attacked in an area aligned to his rival, Alassane Ouattara, who is recognised by the UN as the winner of last year's polls.
On Monday, witnesses said soldiers shot at supporters of Mr Ouattara during demonstrations, killing at least six.
An African Union-backed panel is in the country to try to resolve the crisis.
It is the AU's latest attempt to mediate the situation in Ivory Coast, which has endured since both Mr Gbagbo and Mr Ouattara each declared victory in presidential elections in November.
Four vehicles belonging to the security forces were ambushed in the Abobo neighbourhood on Tuesday. "All the occupants were killed," a security source told the AFP news agency.
A medical source said at least two injured troops were admitted to hospital, the report added.
The clashes in Abobo were said to have continued for most of the day, witnesses said.
Meanwhile, the AU panel of four African presidents - from South Africa, Tanzania, Chad and Mauritania - met Mr Ouattara on Tuesday after travelling to Abidjan earlier this week.
"Your mission is for us a last-chance mission because seven others have come before you," Mr Ouattara told them, AFP reported.
The South African government, whose President Jacob Zuma is a panel member, said their proposals focus on the creation of a power-sharing interim government until new elections can be held.
The panel met with Mr Gbagbo on Monday.
At least six people were killed on Monday when troops opened fire on demonstrators calling for Mr Gbagbo to step down, witnesses said.
Violence has continued to escalate since the elections, with Amnesty International warning on Tuesday of a "human rights black hole" in the country.
The human rights organisation says it has evidence of rape and extrajudicial killings being committed by both sides.
"The eyes of the world may have shifted from the political stalemate... but the abuses are clearly continuing," Gaetan Mootoo, one of the Amnesty researchers, said in a statement.
About 500 people, mainly pro-Ouattara supporters, have been killed since the election results were announced at the beginning of December, the UN says.
November's presidential vote was supposed to reunify the West African nation, which has been divided between north and south since a conflict in 2002.