South African authorities have detained a Russian cargo vessel suspected of carrying illegal arms.

According to Herald Live, authorities discovered explosives on board the vessel in the course of operations at the Port of Ngqura, just off the coast of Port Elizabeth.

The illicit cargo was said to be headed for Nigeria and US, the report said.

The explosives and weapons — reportedly valued at about R50 million — were discovered following a tip-off, after the ship had offloaded 14 containers at the port.

The containers were reportedly dispatched by a company named Solar India.

The tip-off was said to have alerted authorities to a further hidden 20 containers where the weapons were hidden.

The Hawks, a South African criminal investigative organisation, is said to have commenced an investigation into the incident.

The vessel, named Lada, is currently anchored 15 kilometres off the Nelson Mandela Bay coastline.

Of late, the Nigerian Immigration Service has been reporting increasing discovery of arms illegally imported into the country.