Five seafarers are missing after their dredger collided with a MR tanker off Singapore early on Wednesday morning.

Seven crewmen were rescued from the upturned Dominican-registered dredger JBB de Rong 19 following the incident with the 30,747-dwt Karitike Segara (built 1998).

The tanker reported damage to her starboard bow, but is stable and anchored at the Eastern Anchorage. Its 26 Indonesian crew did not sustain any injuries.

Singapore's Maritime and Port Authority (MPA) said it was notified of the collision at about 12.40am (Singapore time) on Wednesday.

The incident is said to have taken place in Singapore territorial waters, about 1.7 nautical miles south-west of Sisters Island.

The dredger was transiting the westbound lane while the tanker was departing Singapore joining the eastbound lane of the Traffic Separation Scheme (TSS) in the Singapore Strait when the incident occurred.

The Singapore vessel traffic information system had provided navigational information to both vessels prior the collision, the MPA confirmed.

The MPA added that it was leading the search and rescue (SAR) operations and relevant Singapore agencies are rendering all assistance.

Two MPA tug boats have moved the partially submerged dredger safely to an area near Pulau Senang for follow up underwater search operations.

In addition, MPA said it had deployed three patrol craft to assist in the SAR operation with another seven craft taking part from other Singapore agencies.

Navigational broadcasts for ships to look out for the missing crew and to navigate with caution when in the vicinity of the incident site have been issued.