(Reuters) - China has accelerated settlement-building along its disputed border with Bhutan, with more than 200 structures, including two-storey buildings, under construction in six locations, according to satellite image analysis conducted for Reuters.

The images and analysis supplied to Reuters by U.S. data analytics firm HawkEye 360, which uses satellites to gather intelligence on ground-level activities, and vetted by two other experts, provide a detailed look into China's recent construction along its frontier with Bhutan.

Construction-related activity in some of the locations along Bhutan's western border has been under way since early 2020, with China initially building tracks and clearing out areas, based on material provided by satellite imagery firms Capella Space and Planet Labs, said Chris Biggers, the mission applications director at HawkEye 360.

Images show the work speeded up in 2021. Smaller structures were erected - possibly to house equipment and supplies - followed by the laying of foundations and then the construction of buildings, Biggers said.

"To me, 2021 was the period for acceleration," Biggers said.

Two other experts who studied the locations of the new construction and recent satellite images taken by Capella Space said all six settlements appear to be in territory disputed by China and Bhutan - including a contested tract of roughly 110 square kilometres - with little in the way of resources or native population.

"It is Bhutan's policy not to talk about boundary issues in the public," Bhutan's foreign ministry said in response to questions from Reuters. The ministry declined to comment further.

The construction suggests that China is bent on resolving its border claims by giving its ambitions concrete form, said the experts and one Indian defence source.

China's foreign ministry said the construction is "entirely for the improvement of the working and living conditions of the local people."

"It is within China's sovereignty to carry out normal construction activities on its own territory," the ministry said. The ministry declined to comment further.

The villages also offer Beijing some strategic value, two of the experts say. The new construction is 9 to 27km from the Doklam area at the junction of the borders of India, Bhutan and China, where Indian and Chinese troops were locked in standoff for more than two months in 2017.