Singaporean authorities said Friday two oil tankers caught fire off its coast and two crew members were airlifted to a hospital.

The blaze broke out on board Singapore-flagged tanker Hafnia Nile and another vessel about 55 kilometres (34 miles) northeast of Pedra Branca, according to Singapore's Maritime and Port Authority (MPA).

"MPA has requested passing vessels to assist in the search and rescue of the crew," the authority said in a statement, adding that the RSS Supreme and a military helicopter were providing assistance.

Two crew members were sent to the Singapore General Hospital, according to a separate statement by the air force posted on social media that did not provide details about their injuries.

Singapore's navy posted photos on Facebook showing thick black smoke coming from the burning vessels and rescued crew members being helped onto the RSS Supreme.