Boris Johnson, the mayor of London, has gone to Kurdistan to examine firsthand the progress being made to push back the forces of Islamic State in Syria and Iraq.

City Hall, in London, declined to give details of the visit, for security reasons, but said the trip was also meant to strengthen economic ties between London and Kurdistan.

Johnson, who travelled in the kind of secrecy only possible if accompanied by the Sun newspaper, was holding high-level talks in Erbil, the capital of Kurdistan, a city once regarded as an island of security, but which has more recently come under threat from Isis forces. At one point Isis took territory just 18 miles from the regional capital.

With every move of the mayor open to interpretation, especially by his arch rival, the home secretary, Theresa May, the visit will raise eyebrows from those who believe he is burnishing his credentials as an international statesman capable of thinking more broadly than the next London police committee meeting.

Ironically, his absence from the capital coincided with the arrival in London of many senior Iraqi leaders to discuss the progress of the fight against Isis. The discussions are being jointly hosted by the foreign secretary, Philip Hammond, and the US secretary of state, John Kerry.

London Mayor Boris Johnson takes aim with an AK47 during a visit to the see the British Troops training the Peshmerga. Photograph: Andrew Parsons / i-Images

Johnson told the Evening Standard newspaper: “I’m going to support some of our guys out there who are trying to train the peshmerga fighters, so we will see firsthand some of the good Britain is doing in the area.”

Johnson has been a long-term supporter of Kurdistan, and his official said: “He wants to see firsthand the work being done to keep Isil [Isis] at bay, the same Isil that wants to send back terrorists who would blow themselves up in London given half a chance.”

In May last year Johnson hosted a visit by Nechirvan Barzani, the prime minister of the fledgling nation state of Kurdistan, and several of his ministers, on a first official trip to the UK. Johnson discussed the Kurds’ plans to build hotels and ski resorts in their country as well as transform Erbil into “the natural banking centre of the Middle East”.

Boris wrote last August: “Standard Chartered Bank has established [itself in Kurdistan], as well as many other firms. They are going not simply because Kurdistan has theoretically the sixth largest oil deposits in the world, but because the place is an oasis of stability and tolerance. They have a democratic system; they are pushing forward with women’s rights; they insist on complete mutual respect of all religions.”

He also took a hard line about British citizens going to Syria or Iraq “without good reason”, adding that they should be subject to surveillance and possibly arrested if they no longer swore allegiance to the UK.