United Nations Secretary-General Antonio Guterres called on Nigerian authorities to investigate allegations of systemic and coerced abortions reportedly perpetrated by the Nigerian army, U.N spokesman Stephane Dujarric said on Friday.

Reuters reported on Wednesday that the Nigerian Army has run a secret, systematic and illegal abortion programme in the country’s northeast since at least 2013.

The programme involved terminating at least 10,000 pregnancies among women and girls, many of whom had been kidnapped and raped by Islamist militants, according to dozens of witness accounts and documentation reviewed by Reuters.

Nigeria’s defence chief said on Thursday the military will not investigate the report, saying it was not true. The Nigerian government has not responded publicly to the story.

Nigeria’s Information Minister Lai Mohammed could not immediately be reached for comment on the U.N. call for an investigation.