The UN's refugee agency (UNHCR) has said it is "deeply concerned" by news that four refugees were returned to Turkey from Kenya.

The four were repatriated at the request of the Turkish government, Kenya's foreign ministry said.

The statement comes after reports of several people being abducted in the capital, Nairobi, on Friday.

A British national told the BBC he and several Turkish citizens had been kidnapped by masked men.

He said he had been released after eight hours when he showed his alleged abductors a copy of his British passport.

In a statement the UNHCR said it "urges the Government of Kenya to abide by their international legal obligations, and in particular, to respect the principle of non-refoulment [forced return of refugees], which protects asylum-seekers and refugees from any measure that could lead to their removal to a place where their life or freedom would be threatened".

Kenya's foreign ministry said it had agreed to Turkey's request to repatriate the four men because of the country's "robust historical and strategic relations" with Turkey, and that it had been assured the refugees would be "treated with dignity".

The four are believed to be followers of the Gulen movement, a powerful Islamic community with followers in Turkey and worldwide, whose leader has just died.

The Gulen movement runs a network of schools in Kenya and around the world.

Known as Hizmet or "service" in Turkey, it was blamed for a 2016 coup attempt and later declared a terrorist organisation.

Turkish authorities have not yet commented on the repatriation.

Under the UN's 1951 Refugee Convention, refugees should not be returned to a country where they face serious threats to their life or freedom.

Following the reported abduction, Kenyan law firm Mukele & Kakai said it was acting on behalf of four men who were registered refugees and warned airlines against allowing them to be taken on board.

In a letter seen by the BBC, it described them as "victims of political victimisation".

The Kenyan government said it had "unswerving commitment to the protection and promotion of refugee rights" and was "committed to the privacy and confidentiality of the repatriated individuals".

The British national, Necdet Seyito?lu, told the BBC six other people he knew - all Turkish citizens - were also abducted in the same manner from different locations in Nairobi.

In a statement, the UK Foreign Office said it was "providing consular support to a British man and his family following an incident in Kenya".

Following reports of the kidnapping, Kenyan police told the BBC they were investigating a "kidnapping incident" after a motorcycle driver witnessed the abduction.

According to the report, two vehicles intercepted and blocked a silver saloon car with two occupants from the front and behind.

"About eight persons armed with weapons emerged from the two vehicles, pulled out the two occupants" and drove off with them, said police spokeswoman Resila Onyango.

However, Amnesty International's Kenya spokesman said he was "deeply concerned by reports that seven asylum seekers from Türkiye have been abducted on Kenyan soil".

The UNHCR told the BBC it was "aware of reports and will provide more information once we have it".

Turkey's relationships with African countries has grown over the past 20 years, with President Recep Tayyip Erdogan seeking to strengthen ties.

But Kenya's close ties with Turkey go even further back.

In 1999, Kurdish separatist leader Abdullah Öcalan was apprehended by Turkish forces in the country and taken back home where he was put on trial, and later convicted, for treason.