At least 24 Nepalese troops and police have been killed by Maoist rebels in the east of the kingdom, the army says.
The rebels have been fighting for a republic since 1995
The bodies of six rebels have also been recovered, although the army says many more Maoists died in the fighting in Ilam district.
All 50 security personnel missing in the area have made contact.
More than 10,000 people have died in Nepal's conflict since the rebels began their fight to replace the monarchy with a communist republic in 1995.
The latest clashes are reported to have followed a rebel ambush of a military contingent that was returning after clearing a roadblock near the Puwa river in Ilam.
An unnamed army official told the AFP news agency that the clashes took place "while the army was trying to remove landmines planted by the rebels" along a road in the area.
The incident came a week after the rebels ignored a government deadline to resume peace talks.
Nepal's authorities want to clear the way for elections to parliament, suspended two years ago because of the violence.
The rebels, who control large swathes of Nepal, have threatened to disrupt the vote.
Many observers doubt that elections can be credible in the current climate.
In a related development, the London-based human rights group, Amnesty International, accused both Nepalese government troops and rebels of committing serious human rights abuses.
In a new report, Amnesty said "unlawful killings" had risen as the conflict had escalated.
A third of casualties had come after peace talks between the government and the rebels collapsed in August 2003, it said.
Amnesty urged government troops and the rebel leadership to investigate the killings and punish those responsible in their ranks.
The authorities and the rebels both deny deliberately committing serious abuses.
They have repeatedly vowed to respect human rights and punish those found guilty of committing abuses.
Amnesty International say it is not convinced.
"These killings are going completely unpunished, despite numerous promises by the government and Maoist leaders to uphold human rights," Ingrid Massage, Amnesty's Asia director, told reporters in Kathmandu.