China's Ministry of Transport has called in Maersk and Mediterranean Shipping Company for talks on "international shipping operations" amid legal battles over Panama Canal ports, reports Hong Kong's South China Morning Post.

The ministry issued a brief statement without further details. In China, government summons are often seen as warnings that can lead to further action if ignored.

The move follows Panama's decision in late February to hand temporary control of Balboa and Cristobal ports to Maersk's APM Terminals and MSC's Terminal Investment.

The Panama Maritime Authority acted after the Supreme Court ruled that CK Hutchison's long-term concession, granted in the 1990s, was unconstitutional. CK Hutchison's Panama Ports Company had operated the facilities until the ruling.