The Iranian-registered Danoosh, weighing 13,914 gross tons, collided with Indonesian-registered containership Lagun Mas (2,900 gross tons) at 3-km southwest of St John's Island, said the Maritime Port Authority of Singapore (MPA), which was alerted to the incident at 2.30 am on Thursday.

The east-bound Danoosh had left Singapore with a cargo of maize, and was crossing the Traffic Separation Scheme (TSS), while 'Lagun Mas' was bound west, transiting the Singapore Strait.

'MPA's Vessel Traffic Information Service (VTIS) alerted both vessels and provided navigational information prior to the collision. MPA also dispatched patrol and emergency response craft immediately after the collision took place," said an MPA statement.

There is no report of pollution or injury, and port operations remain unaffected, said MPA.

Danoosh, which has a crew of 33, reported damage to cargo hold, but is in a stable condition, according to MPA. As a precautionary measure, it was shifted to a more shallow area, for salvage works to be undertaken.

It is currently anchored in the Eastern Working Anchorage. But it was seen to be listing earlier on Thursday.

It is said to have intentionally beached on Singapore's Outer Shoal - located 15km off Singapore - in a bid to stop it from sinking.

Salvage company, Svitzer Salvage Asia, has been hired to carry out the salvage operation.

Lagun Mas only suffered damage to its railing and starboard side bow section, and has continued its voyage, said the MPA, which is investigating the cause of the collision.