Amnesty International has voiced alarm over a “sharp rise” in crimes committed by the Nigeria-based Boko Haram terror group, saying attacks by the Daesh-linked militants have claimed nearly 400 civilian lives since April.

In a statement on Tuesday, the UK-based rights group said Boko Haram has increasingly been using bombers, mainly young women and girls, to set off explosives in crowded areas in Nigeria and neighboring Cameroon.

Such bombings, it said, has killed at least 381 civilians in the two countries since April.

“Boko Haram is once again committing war crimes on a huge scale, exemplified by the depravity of forcing young girls to carry explosives with the sole intention of killing as many people as they possibly can,” Alioune Tine, Amnesty’s director for West and Central Africa, said.

Tine further said the “sharp rise” in Boko Haram’s “shocking” acts of violence “highlights the urgent need for protection and assistance for millions of civilians... Governments in Nigeria, Cameroon and beyond must take swift action to protect them from this campaign of terror.”

According to Amnesty, at least 223 civilians have died in Nigeria since April, underscoring that the real toll could be far higher.

“Between May and August, seven times more civilians were killed than in the preceding four months, while 100 civilians were killed in August alone,” the statement said.

On August 22, the United Nations Children’s Fund (UNICEF) expressed “extreme” concern about the “appalling” rise in the use of children as “human bombs” by Boko Haram, which is mainly based in northeastern Nigeria.

The Takfiri group’s terror campaign in Nigeria, which is in its eighth year, has so far killed more than 20,000 and forced the displacement of over two million people. Boko Haram pledged allegiance to the notorious Middle East-based Daesh terrorist outfit in March 2015.

Nigeria’s President Muhammadu Buhari said earlier this year that Boko Haram had been technically defeated, and that the group could no longer pose a threat to major urban centers in northern Nigeria. However, the group continues to launch attacks in the country.

The United Nations has warned that around 8.5 million people in the worst affected areas of northeastern Nigeria are now in need of humanitarian assistance.

In neighboring Cameroon, at least 158 civilians have died in Boko Haram assaults since April, a figure four times higher than the preceding five months, Amnesty said.

In the most recent assault, a group of knife-wielding Boko Haram terrorists carried out a stabbing attack against people in the Cameroonian town of Banki on September, killing at least 18 people.

In July, 16 Cameroonian civilians were killed and at least 34 more injured after a young girl was forced to detonate a bomb in a crowded video game center in the town of Waza.

Besides Cameroon, Boko Haram terrorists also stage attacks in Niger and Chad.