A seized shipment of missile parts en route to Syria was believed to have come from North Korea in what seems to have been a violation of UN sanctions on Pyongyang, diplomats said on Tuesday.

South Korean officials briefed the Security Council’s North Korea sanctions committee about the seizure of the shipment of 445 graphite cylinders – a material usable in a ballistic missile programme – from a Chinese vessel at the port of Busan, Reuters reports.

The graphite cylinders were declared as lead piping intended for a Syrian company called Electric Parts.

“It appears the cylinders were intended for Syria’s missile programme,” a diplomat said. “China assured us they will investigate what looks like a violation of UN sanctions”.

Another diplomat claimed that the crew of the Chinese ship had no idea what the shipment contained and praised Beijing’s willingness to investigate the incident.

Chinese foreign ministry spokesman Hong Lei told the Financial Times that China strictly followed UN resolutions and its own non-proliferation export controls.

According to UN Security Council diplomats, the shipment was arranged by a North Korean trading company. “The DPRK continues actively to defy the measures in the UN sanctions resolutions,” the panel said in May.

North Korea is barred from importing or exporting nuclear and missile technology under UN Security Council sanctions following its nuclear tests in 2006 and 2009.