Up to 180 people are now missing or feared dead after a ferry capsized in Indonesia.

The revised figure, which is far more than officials originally estimated, comes after the sinking at a popular lake on Sumatra earlier this week.

Distraught relatives pleaded for a bigger search effort and were outraged at the government’s failure to enforce basic safety measures on passenger boats.

The wooden vessel, overcrowded with passengers as well as dozens of motorbikes, didn't have a manifest.

Disaster officials have several times raised the number of people it was carrying as family members who rushed to Lake Toba in northern Sumatra provided information.

Only 18 survivors have been found — in bad weather within hours of the sinking Monday evening.

However, North Sumatra province police chief Paulus Waterpa, said it’s possible many of the victims were still inside the sunken ferry.

"Many survivors told authorities that less than half of them had jumped into the water before the boat sank," he said.

One woman, Suwarni, whose 20-year-old son and his girlfriend were on the ferry, slammed the search and rescue operation as slow and insufficient.

"Millions of questions keep me from sleeping," she said.

"Why (is) a boat for just 50 people is allowed to be loaded with almost 200 people plus dozens of motorcycles?

“What kind of government is this that can't protect their own people from unnecessary accidents? And after the accident they're not able to find the victims.

"I beg help to everyone to quickly find my son and his girlfriend, even if their remains, please find my son, return him to me."

Divers were searching at depths of 25 meters and will deploy an underwater drone to 200 meters below the surface.

The 1,145-square-kilometre Lake Toba, formed out of an ancient super volcano, is a popular sightseeing destination on the island of Sumatra. It's more than 400 metres deep.

The search and rescue effort involving 350 personnel and at least half a dozen boats has turned up items of clothing, bags and traces of oil from the ferry but just several victims.

Hisar Turnit, a spokesman for the search and rescue agency in nearby Medan, said three deaths were now confirmed after two more bodies were found this morning.

A rescuer, who didn't give his name, said the dead woman was found about 7 kilometers from where the boat sank.

Mobile phone footage released earlier in the week by the National Disaster Mitigation Agency showed the crew of another ferry attempting to rescue people struggling in the waters shortly after the sinking but being hampered by bad weather and rough waters.

The disaster has cast a tragic pall over holidays marking the end of Ramadan when tens of millions of Indonesians return to their hometowns.

Ferry tragedies are common in Indonesia, an archipelago of more than 17,000 islands, with weak enforcement of safety regulations often to blame.

A grief-stricken Muhaimin, 61, said he had lost eight members of his family including two sons, their wives and children.

"My sons, my daughter-in-laws and my grandchildren have been the victims of greedy businessmen who just want to take advantage of the holiday season without thinking of people's safety," he said. "It would not happen if they follow the rules. But they made money over our misery."