Nelson the griffon vulture (pictured) was captured in Yemen over fears it was being used to spy on pro-government forces there

A vulture has been captured by a militia in Yemen who feared the migrating bird was a spy.

The juvenile griffon, known as Nelson, was seized in the city of Taiz after it apparently became separated from its fellow migrating vultures.

The bird had a GPS tracker attached to its leg when it set off from Bulgaria as part of an environmental group's effort to reintroduce it to the wild.

But militants in the Yemeni city spotted the transmitter and feared it was being used to spy on them during the country's long-running civil war.

Pro-government forces in the city who are battling against Iranian-backed rebels took the bird into captivity, according to The Times.

The Fund for Wild Flora and Fauna said it had received hundreds of messages from Yemenis concerned for the bird's welfare.

'Our team is in contact with local nature conservationists there and we hope the vulture will be rehabilitated and come back to Bulgaria,' the group said.

The bird, hatched in 2018, had been released in Bulgaria's Kresna Gorge last November.

The GPS tracker followed the vulture as it flew over Turkey and into Yemen to migrate to warmer temperatures for the winter.

Yemen’s civil war has been raging since March 2015, with a Saudi-led coalition fighting Iran-aligned Houthi rebels in the Middle East state.

A map showing the bird's migration from Bulgaria before it was captured in Yemen

Nelson, pictured, had a GPS tracker attached to its leg when it set off from Bulgaria as part of an environmental group's effort to reintroduce it to the wild

According to the United Nations, 22 of the country's 29million people are in need of aid.

An air strike by the Saudi-led coalition that killed dozens of people in Yemen last August was branded an apparent war crime by Human Rights Watch.

Yemen has also witnessed two outbreaks of cholera and acute watery diarrhea since 2016.

Yesterday President Donald Trump vetoed a bill passed by Congress to end U.S. military assistance for the Saudis in Yemen.

Mr Trump has been under pressure over relations with Saudi Arabia since the kingdom was accused of murdering dissident journalist Jamal Khashoggi last year.