The nuclear industry has appealed to Kazakhstan to "uphold the sanctity" of uranium contracts amid an investigation of the country's national nuclear company.

Letters this week from the World Nuclear Association (WNA) and the US Nuclear Energy Institute (NEI) to Kazakh President Nursultan Nazarbayev both expressed concern after the arrest of Moukhtar Dzhakishev, the head of KazAtomProm, as well as four other senior executives.

The WNA called for a "just resolution" that "upholds the sanctity of contracts fairly and properly made" and facilitates continued cooperation between Kazakhstan and the global nuclear industry. Both bodies urged Nazarbayev to avoid any disruption to plans for uranium supply or mine development.

Kazakhstan is one of the world's major uranium producers and is to become the leading exporter in coming years thanks in part to a range of joint venture agreements with uranium buyers and traders from around the world.

The KazAtomProm executives are being investigated along with other figures for the alleged 'stripping' of state assets during sales of uranium desposits to investment companies that were later bought into by foreign firms.