Pirates attacked a South Korean-flagged cargo ship in the South China Sea on Monday morning, assaulting the crew and making off with thousands of dollars in cash, China News Asia (CNA) reported.

Two people sustained minor injuries when seven pirates boarded the CK Bluebell and made off with US$13,000 and belongings including mobile phones, clothes and shoes from the 22-strong crew, South Korea’s Ministry of Oceans and Fisheries added.

The dry bulk vessel CK Bluebell had set sail from its anchorage off Singapore late Saturday afternoon, heading northeast for South Korea’s Incheon port, according to Refinitiv Eikon ship tracking data.

South Korean officials said the ship was sailing normally after the robbery, the CNA report said.

Yonhap news agency had reported that the armed pirates attacked the cargo ship near the Singapore Strait.

Responding to CNA queries, the Maritime and Port Authority of Singapore (MPA) said the robbery did not take place in Singapore waters.

“In response to media queries on the incident involving South Korea-registered bulk carrier CK Bluebell, MPA was informed by the Korea Coast Guard that it took place in the South China Sea near Anambas Islands,” said a spokesperson for the authority.

Piracy has fallen in the busy sea lane that runs past Singapore, Malaysia and Indonesia in recent years amid heavier policing.

Earlier this month, MPA said there had been no information on immediate threats to ships sailing through the Straits of Malacca and Singapore or to Singapore-registered ships.

The authority was responding after China raised its security warning to the highest level for its vessels heading through the Straits of Malacca. China did not give a reason for the raised alert, according to Bloomberg.

In May, Defence Minister Ng Eng Hen warned that piracy and terrorism were among threats to maritime security.

While the number of piracy and armed robbery incidents along the Strait of Malacca fell from 20 in 2007 to eight so far this year, “more work needs to be done” on terrorism threats, he said.

He added that experts believe that most of the weapons used by militants during the recent conflict in Marawi came from the sea.

Other Islamic State-linked terrorists like the Abu Sayaff group also continue to abduct the crew of transiting ships in the Sulu-Celebes Sea and the waters off East Sabah in exchange for ransom.