In this Dec 9, 2018 file photo, Dr. Denis Mukwege from Congo prepares to listen to questions, with Nadia Murad from Iraq (not in frame), at a media conference for the 2018 Nobel Laureates at the Nobel Institute in Oslo, Norway. (HEIKO JUNGE / NTB SCANPIX VIA AP)

GENEVA - The life of a top Congolese doctor who won the Nobel Peace prize for his work treating war rape victims is in danger after a series of death threats, the UN High Commissioner for Human Rights said on Friday.

The threats, received in the form of phone calls to Dr. Denis Mukwege and his family as well as via social media, appeared to be linked to his outspoken criticism of violence against women and other human rights violations, a UN official said

The threats, received in the form of phone calls to Dr. Denis Mukwege and his family as well as via social media, appeared to be linked to his outspoken criticism of violence against women and other human rights violations, another U.N. official said.

“His life seems to be at serious risk,” High Commissioner for Human Rights Michelle Bachelet said in a statement, calling for an impartial investigation into the threats.

Mukwege received the Nobel Peace Prize in 2018 for his work as a gynaecologist at the Panzi hospital which receives thousands of women each year, many of them requiring surgery from sexual violence.

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The hospital is located in eastern Democratic Republic of Congo where ethnic violence is rife, involving various militia and armed groups, as well as counter-operations by the army.

He has received death threats before and survived an assassination attempt in his family compound in 2012.

“The threats appear to be linked to his advocacy and the very robust positions he has taken on accountability, on protection of women as a result of what he has seen over two decades in the Panzi hospital,” said Rupert Colville, a spokesman at Bachelet’s office, adding that he had also recently criticized civilian attacks in South Kivu.

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Congo’s government is officially responsible for Mukwege’s protection, although the UN peacekeeping mission in the country also provides some, Colville said. However, questions remain about the quality of his protection, he said, adding he needed 24 hour surveillance.

President Felix Tshisekedi last week called on his government to take all necessary measures to ensure his security and to open inquiries into the threats against him.