Philippine peacekeepers trapped by rebels in the Syrian Golan Heights are "under attack", Philippine Defence Minister Voltaire Gazmin says.
He said the assault had started early on Saturday, but gave no details on any casualties.
In recent days the Syrian rebels have taken 44 Fijian peacekeepers hostage in the area and surrounded 75 Filipinos manning two separate UN posts.
The rebels have also seized a crossing point into the Israeli-occupied Golan.
They are believed to include members of the al-Nusra Front, al-Qaeda's affiliate in Syria.
Mr Guzman told reporters that 40 Philippine soldiers trapped at one post had come under attack on Saturday.
Thirty-five others based at the other camp have been "extricated", he said.
The Fijian members of the UN Disengagement Observer Force (Undof) were detained on Wednesday near Quneitra, during fighting between rebels and government forces.
Last week the Philippine government said it would bring home its 331 peacekeeping forces from the Golan Heights in October, amid deteriorating security there.
Israel seized most of the Golan Heights, a strategic plateau in south-western Syria, during the 1967 Six-Day War.
The two countries signed an armistice in 1974, after which Undof was put in place to monitor the demilitarised zone.
It has 1,224 lightly-armed military personnel from Fiji, India, Ireland, Nepal, the Netherlands and the Philippines.