Indonesia has reported a new cluster of 42 coronavirus infections among medical workers who treated 13 Filipino ship crew who were sick with Covid-19, and is tracing dozens of others, a government official said.

About 140 other medical workers came into close contact with the crew of Panamanian-flagged cargo ship Hilma Bulker who tested positive for the new coronavirus after docking in Central Java on April 25, Ganjar Pranowo, the governor of the Central Java province, told Reuters. The vessel had come from India.

Genome sequencing showed the crew had the highly infectious B.1617.2 variant first identified in India, Ganjar said, adding that one of them had later died in hospital.

"For now we're actively tracing their nurses. Hundreds had had direct contact, close contact, and 42 had tested positive," Ganjar said by phone.

Ganjar said all other crew members of the Hilma Bulker had self-quarantined on the ship, and 49 Indonesian officials who oversaw the unloading of the ship had all tested negative for the virus.