UN peacekeepers on Thursday patrolled a security zone in a eastern Democratic Republic of Congo city where they have given militia fighters an ultimatum to disarm, a spokesman said.
The UN mission in the country, known as MONUSCO, had given the M23 rebels and other armed groups inside the zone in Goma until Thursday to lay down their weapons.
MONUSCO had said it was ready to use "force" to disarm fighters, who are accused of being behind a new surge in violence in the volatile region.
But the United Nations gave no immediate indication that military action had started or was planned.
"MONUSCO peacekeepers are patrolling across the security zone in support of the Congolese armed forces," said UN peacekeeping spokesman Kieran Dwyer.
"This will be an ongoing operation to protect civilians in a densely populated area," he added.
The security zone takes in Goma and northern suburbs including a neighboring town of Sake.
M23 rebels launched a new offensive against the army near Goma on July 14 but the area has been calm in recent days.