Image copyright Andrew Maher/MarineTraffic.com Image caption Two of the crew on the CK Bluebell sustained minor injuries

Armed pirates have stormed a South Korean cargo ship in the South China Sea, stealing thousands of dollars and the sailors' shoes.

The seven pirates - who were armed with guns and knives - attacked the CK Bluebell on Monday and took $13,000 (£10,400) cash, mobile phones, clothes and even the crew's footwear.

Two of the 22-strong crew suffered minor injuries during the raid.

South Korean officials said the vessel was sailing normally after the attack.

"Seven pirates, including one carrying a gun and two armed with knives, got on board and assaulted the sailors for about 30 minutes," an official at the Ministry of Maritime Affairs and Fisheries told the Yonhap news agency.

The CK Bluebell had set sail from its anchorage off Singapore on Saturday, heading towards the South Korean port of Incheon before it was attacked near the Singapore Strait, which passes Indonesia, Malaysia and Singapore.

Singapore's Maritime and Port Authority (MPA) said the incident did not take place in city-state's waters, but near the Anambas Islands, an archipelago of Indonesia.

Policing has been ramped up on the route in recent years, resulting in less piracy.

However, piracy has seen an increase on the world's seas, with the International Chamber of Commerce recording 201 incidents of maritime piracy and armed robbery in 2018, up from 180 in 2017.

The South China Sea is home to vital shipping lanes, but in recent years has also become a flashpoint for tensions between China and several regional nations which have overlapping claims over islands and reefs.