Residents in a rural Turkish village have expressed their pride and joy at seeing Boris Johnson, whose ancestry can be traced back there, becoming the UK's new prime minister.

Kalfat, located 100 kilometres north of the capital Ankara, was the birthplace of Johnson's great-great-grandfather, Haci Ahmet Riza Efendi (Efendi is an Ottoman title of respect) in 1813.

On Tuesday, after it was announced that Johnson had won the Conservative Party's leadership contest, some of Kalfat's 1,300 residents celebrated by gathering in the main assembly place, according to town's administrator, Bayram Tavukcu.

A day later, Theresa May officially resigned and Johnson replaced her in 10, Downing Street.

"For a person who came from these lands ... to be at the top of a playmaker country like Britain as the prime minister has led us to feel sentiments that we cannot describe," Tavukcu told the Associated Press.

Adem Karaagac, one of Kalfat's residents, said locals "would like Boris Johnson to visit his ancestral lands. We would be pleased and honoured to host him."

Satilmis Karatekin, a distant cousin of the new British leader, concurred: "We want him to visit his ancestral lands, to visit us and honour us."

They dismiss Johnson's past criticism of the country as politically necessary.

In 2016, he won a contest organised by the Spectator magazine — for which he had previously been the editor — to write the most offensive poem they could on Turkish president Recep Tayyip Erdogan.

In the lead up to the 2016 Brexit referendum, Johnson also repeatedly raised the idea that Turkey could join the European Union, which he said would lead to Turkish people emigrating to the UK.

"He had to say such things in the political arena, in order to make political gains. You know as well as us and all politicians know it as well. The people in his country know it too," Mustafa Bal, a former mayor of Kalfat, said.

Johnson has also used his Turkish heritage to bat away accusations of Islamophobia, arguing last month during a leadership debate that his "Muslim great grandfather" would have been proud to see him become foreign secretary.

Ahmet Riza Efendi's son - Johnson's great grandfather - was the Ottoman political journalist Ali Kemal who later became an interior minister. Considered pro-British and a "traitor" he was killed by a mob in 1922, during Turkey's war of independence.

Kemal's son, Osman Wilfred - Johnson's grandfather - was raised by his maternal grandmother, Margaret Johnson, in Britain after Kemal's Swiss-British wife died.