Image copyright Courtesy of the Squire family Image caption Ian Squire was kidnapped in southern Nigeria in October

A British aid worker kidnapped last month in southern Nigeria has been killed, while three other hostages have been freed, says the Foreign Office.

Ian Squire, an optician, was one of four Britons working for a medical charity in the Niger Delta when taken.

Suspected militants stormed the rural community of Enekorogha on 13 October.

UK and Nigerian authorities successfully negotiated the release of Alanna Carson, David Donovan and Shirley Donovan.

BBC Lagos correspondent Stephanie Hegarty said there was little detail around Mr Squire's death, but that locals told her the kidnappers were a criminal gang who had been operating in the area for around a year.

Our correspondent said: "This is their first kidnapping of foreigners. They had kidnapped very recently the mother of a local politician, but before that they were just carrying out petty crime.

"We know that a ransom was demanded but we don't know if it was paid."

Established charity workers

According to reports, Dr and Mrs Donovan have lived in Nigeria for the past 14 years, running a Christian charity called New Foundations, which gives aid to remote villages in the Niger Delta.

Image copyright Courtesy of the Donovan family Image caption Dr and Mrs Donovan (pictured) were released and are now home safely

Mr Squire normally ran a practice in Shepperton, Surrey, and locals told the BBC he travelled to Africa every year to carry out charity work.

Mr Squire's friend Paul Allan, who ran a neighbouring business, described him as a "good friend" and a "very straight forward, nice, gentle guy".

He described how Mr Squire fundraised in the community for his trips and even collected old glasses to take and reuse.

"I just can't believe what's happened," added Mr Allan. "I find it shocking to believe for someone who has gone out to do good in the community overseas that the action has cost him dearly. It has cost him his life. It is beyond belief.

"It is a sign of this day and age, but he wasn't concerned about that. He just wanted to go out and help people in less fortunate situations than ours."

Image copyright BBC news online

Ms Carson, a Specsavers optometrist, is now staying with her family in Northern Ireland, according to her employer in Leven, Fife.

Relatives of the four said they were "delighted and relieved" that Ms Carson and Dr and Mrs Donovan had returned safely.

"Our thoughts are now with the family and friends of Ian as we come to terms with his sad death," they said in a statement issued on their behalf.

Image copyright Courtesy of the Carson family Image caption Ms Carson (pictured) was working alongside Mr Squire

The Foreign Office currently advises against all but essential travel to much of Delta state, saying there is a "high threat of criminal kidnap".

It said Nigerian authorities were investigating the kidnapping, adding: "Our staff will continue to do all we can to support the families."