A government plane in Yemen bombed its own troops in the south of the country on Saturday, killing at least 18 soldiers.
The BBC reports the bombing on Saturday evening hit 119th brigade troops near Zinjibar in Abyan province and was followed by attacks by rebels.
It is unclear how many died in the actual bombing, or if it was an error.
However, Yemeni TV said no such air strike had taken place.
Reports say the 119th brigade has joined a rebellion against President Ali Abdullah Saleh.
Protesters rallied in Sanaa on Sunday to demand his removal.
Hundreds of people have been killed since protests began in January.
There were also reports of gunfire near the base of rebel General Ali Mohsen.