The EU has expressed concern over a deepening corruption scandal in Turkey that has ensnared prime minister Recep Tayyip Erdogan's allies, and urged the country to handle the issue in a "transparent and impartial manner".

The statement came amid claims the government is trying to stifle the corruption investigation. Its attempt to change regulations on how probes are conducted was overturned by a Turkish high court, a move welcomed by the EU's Enlargement Commissioner, Stefan Fuele, who said the change undermined the judiciary's capacity to act.