GENEVA (Reuters) - The Houthi militia group which controls much of Yemen including the capital Sanaa has barred without explanation the head of the U.N.’s human rights office in Yemen from returning to the country, a U.N. spokeswoman said on Friday.

Elobaid Elobaid, a Canadian citizen, had been based in Yemen since October 2016, leading a team of 17 staff in Sanaa and 13 monitors in 11 of Yemen’s governorates. His visa expired in June but was not renewed.

The Iran-allied Houthis have been fighting against Yemen’s internationally-recognised government and a Saudi-led coalition since 2015.

“The de-facto authorities in Sana’a in June refused to renew the visa of the head of the UN Human Rights Office, and since then he has been unable to re-enter the country,” U.N. human rights spokeswoman Liz Throssell told reporters in Geneva.

“They provided no reason for their decision and our requests for them to reconsider have, to date, gone unanswered. This has heightened our concerns for the safety of our staff and field monitors in Sanaa and other governorates across Yemen, and we urge the Houthis to reverse their decision.”

The U.N. human rights office has frequently criticized the Houthis for indiscriminate shelling and sniping and the use of child soldiers, but it has also often blamed the Yemeni government and the Saudi-led coalition, and accused all sides of violating international law and committing war crimes.

On Friday the Houthi group said 40 children were among those killed in an air strike on a bus in north Yemen by the Saudi-led coalition. The coalition said it would investigate. [nL5N1V11MI]