JAKARTA - An overloaded ferry sank in bad weather off Indonesia's Riau islands on Sunday, killing four while nearly 300 passengers survived the accident, officials said.

A transport ministry official told a news conference in Jakarta the ferry, which had the capacity to carry 273 people, had 213 passengers on its manifest. Sunaryo, director general of sea transportation, said 292 people had survived.

The disparity between the manifest and reality is large, it's such a classic case of breaking the regulations, said Sunaryo.

Bad weather is hampering search and rescue efforts. The waves are as high as six meters, it's difficult for small ships to reach the location.

The ferry, the Dumai Express 10, was sailing from Batam near Singapore to Dumai island in Riau when it ran into massive waves, Riau police chief Puji Hartanto told Metro TV.

Survivors were spotted floating at sea, Hartanto said.

Separately, another ferry, the Dumai Express 15 with 278 people on board, ran aground after it was hit by large waves, said Riau police spokesman Yasin Kosasih.

All passengers and crew survived, he added. The ferry was traveling between Batam and Moro island.

Indonesia relies heavily on ferry services to connect the many islands in the sprawling archipelago.

But accidents are common, largely due to years of under-investment in infrastructure and a tendency to overload ferries.

(Writing by Sara Webb; Editing by Sugita Katyal)