It is feared the hunt for Samantha Lewthwaite, described as the world's most-wanted woman, may have "gone cold" after she reportedly underwent plastic surgery to evade capture.

Lewthwaite, 28, dubbed the 'White Widow', has been on the run for the past three years after being accused of a series of terrorist offences in Kenya.

Detectives responsible for finding the British Muslim convert were summoned to a court in Mombassa and ordered to give an update on the search.

Police admitted they had lost track of Lewthwaite after she allegedly altered her appearance.

A police source granted anonymity for fear of reprisals told The Sun: "She is a person with multiple identification. She keeps on moving."

The source added: "We think she is using plastic surgery on her face, including her nose."

There have also been unverified reports Lewthwaite had shed weight in order to help transform her appearance.

Lewthwaite, widow of 7/7 Kings Cross bomber Germaine Lindsay, is accused of a bomb attack in Mombasa with fellow British accomplice Jermaine Grant in December 2011.

She is also said to have ties with the Islamist militant group al-Shabab, the al-Qaeda-linked terrorist organisation behind the attack on Nairobi's Westgate shopping centre in Kenya in 2013. Sixty-eight people were killed in the attacks.

There have been several reported sightings of Lewthwaite down the years in both Kenya and neighbouring Somalia.

She was reportedly spotted in a Somalia forest in May being protected by a group of al-Qaeda fighters known as the Istishhadyin unit –a suicide squad who have orders to protect her to the death.

There was also speculation in June that a white woman had been offered a police escort to visit a Kenyan army base in Somalia. Police dismissed these allegations, saying the woman had been a Spanish tourist.

The 30-year-old, originally from Aylesbury in Buckinghamshire, is also said to have married a senior commander in al-Shabaab Hassan Maalim Ibrahim, also known as Sheikh Hassan.