YAOUNDE -- At least two people died and 20 others were injured in an explosion on Sunday in Cameroon's restive Anglophone region of Northwest, according to witnesses and local police.

The blast occurred in Nkambe, a town in the region, as school children were taking part in activities to mark National Youth Day, which has been celebrated in the country on Feb 11 since 1966.

Many of those affected were schoolchildren.

Health workers were "working very hard" to treat many of the children who sustained "very serious" injuries, a security source in the region told Xinhua.

"The death roll could increase. It is a disturbing situation but our brave soldiers have beefed up security to track down the terrorists who committed this abominable act," the source said.

Authorities were yet to make an official statement.

Separatists had imposed a three-day lockdown to disrupt the activities in the regions where they have been clashing with government forces since 2017 in a bid to create an independent nation they call "Ambazonia."