Terror suspect Samantha Lewthwaite is feared to be at the centre of a major new al-Qaeda plot in the Yemen.

Intelligence officials fear the “White Widow” – who was married to 7/7 suicide bomber Germaine Lindsay – is involved in plans to hit targets there, which last week led to the closure of the British embassy.

Now a crack team of SAS and ­specialist terror police searching for Lewthwaite – the world’s most wanted woman – has been beefed up in an all-out attempt to capture her. She has been on the run since ­Christmas 2011.

A security source said: “Samantha Lewthwaite is known as a key figure in this region in helping raise funds to facilitate terrorist activity.

"With the increased situation in the Yemen, ­officials fear she will play a key role, and extra ­resources are being allocated to find her.

"The view remains that ­capturing her will help reduce the risk to Westerners in the region.”

It is believed that Lewthwaite, 29, originally from Aylesbury, Bucks, has made drastic changes to her appearance.

She is thought to have lost two stone and, although she wears a headdress, ­regularly ­changes her hair colour.

She converted to Islam in her teens, taking the name Sherafiya. She married ­Lindsay in 2002 after they met on the internet, and was seven months pregnant with their second child when he blew himself up at King’s Cross station.

Lewthwaite initially ­condemned the 7/7 attacks, but slipped off the radar in 2007.

She is now believed to be a vital conduit between al-Qaeda groups in Pakistan and East Africa.

She is also thought to have channelled funds raised in the UK and elsewhere to terrorist groups in Somalia.

She is accused of ­involvement in grenade ­attacks in the Indian Ocean resort of ­Mombasa – one of which killed a nine-year-old boy – and is reported to have used Twitter to try to launch an all-female suicide squad.

Last week all British ­diplomatic staff in Yemen were ordered back to the UK. British nationals had ­previously been advised against all travel to Yemen and those in the country were urged to leave ­immediately.

The Foreign Office said: “Due to increased security concerns, all staff in our Yemen embassy have been temporarily withdrawn, and the embassy closed until staff are able to return.”

Yemeni intelligence ­services found that tens of thousands of al-Qaeda ­members have arrived in the capital Sanaa this week.