The United Nations (UN) says the latest wave of terrorist attacks by Takfiri Boko Haram militants in northeastern Nigeria has forced around 20,000 people to flee their homes to other countries.

The UN High Commissioner for Refugees (UNHCR) said Tuesday that more than 11,000 people have fled to neighboring Chad following the attacks by the Takfiri group earlier this month. The rest have sought shelter in Niger and Cameroon, it added.

The mass displacement comes after a number of towns and villages came under attack in the northeast of Nigeria. On January 3, the Boko Haram militants stormed the town of Baga in Borno State and razed it along with at least 16 surrounding settlements.

Ravina Shamdasani, a spokeswoman for the UN High Commissioner for Human Rights (UNCHR), told reporters in Geneva on Tuesday, "We deeply deplore the vicious, ruthless attacks against civilians in... Baga.”

She said it appeared “fairly certain... that mass killings and mass forced displacement have occurred.”

“The deliberate targeting of civilians is clearly prohibited by international law and we are very concerned at reports that there were children and elderly people among the victims,” Shamdasani said.

Amnesty International estimates that around 2,000 people have been killed in attacks in Baga near the country’s border with Chad. The Nigerian government puts the number at around 150.

The UN has condemned the mass killing of civilians as vicious and ruthless.

Boko Haram, whose name means “Western education is forbidden,” has claimed responsibility for a number of deadly shooting and bombing attacks in various parts of Nigeria since 2009.

According to some reports the violence, which has forced 1.5 million people to flee their homes, killed over 10,000 people last year alone.