At least 15 people are dead and 28 missing after an inter-island ferry carrying at least 350 people sank early Monday morning in waters off Basilan Province in the southern Philippines, The Philippine Star reported, citing the Philippine Coast Guard (PCG).

In an interview with One News, PCG spokesperson Noemie Cayabyab reported at least 15 fatalities, 28 missing and 316 survivors, The Philippine Star reported.

Romel Dua, a coast guard commander based in southern Mindanao, meanwhile told AFP that the figures were still being validated.

The PCG said the MV Trisha Kerstin 3 was en route to Jolo Island in Sulu Province from Zamboanga City when it sank before 2 a.m. on Monday off Balukbaluk Island in Hadji Muhtamad, a municipality in the Sulu Sea.

"The search and rescue operation is ongoing, but what I can say is that the ship is not overloaded. It has a maximum passenger capacity of 350, and the actual passengers on board, as declared by the master, are 332," PCG Chief Admiral Ronnie Gil Gavan told reporters in Manila.

Gavan added that the PCG has immediately acted on the incident, saying that all rescue assets in the region are involved.

"There are casualties, but the details are not yet final," Gavan said, adding that the cause of the sinking was still under investigation. 

Sea accidents are frequent in the Philippine archipelago, primarily due to frequent storms, poorly maintained vessels, overcrowding and inconsistent enforcement of safety regulations, particularly in remote provinces.

One of the most devastating incidents in recent history occurred in December 1987, when the ferry Dona Paz collided with a fuel tanker in the central Philippines, resulting in the deaths of more than 4,300 people, making it the deadliest peacetime maritime disaster in the world.