Eighty five people were injured Friday, three of them seriously, when a high-speed ferry travelling from Hong Kong to Macau hit an unidentified object in the water, authorities said.

The nighttime crash, which took place on a popular tourist route, comes at a time of heightened public concern over the safety of maritime transport in Hong Kong's harbour, one of the world's busiest shipping lanes.

Last month the city marked the one-year anniversary of a ferry collision which claimed 39 lives, Hong Kong's worst maritime disaster for over 40 years.

In the latest incident, the double-deck hydrofoil "Madeira" carrying 105 passengers and 10 crew "collided with an unidentifiable object" around 1:15am (1720 GMT) near one of Hong Kong's small outlying islands, boat operator TurboJet said.

Passengers described being hurled out of their seats by the force of the collision.

"There was suddenly a loud bang. The ferry was thrown upwards. Then many passengers were thrown out from their seats," one passenger identified as Mr Wong was quoted as saying by Hong Kong's Apple Daily.

Multiple passengers were stretchered into ambulances by emergency services staff, some wrapped in neck braces and breathing through oxygen masks. The walking wounded limped away in bandages after treatment at the scene.

One passenger told Hong Kong television that the crash felt like a heavy collision.

"Big, very big, I could hear the sound 'Bang'," he said.

Three fireboats were scrambled to search the scene but failed to find any object in the water, fire officials said.

Of those hospitalised, three were still being treated for serious injuries.

"As of 6am this morning we know 85 people were injured, three of whom are in a serious condition," a Hong Kong government spokeswoman told AFP.

She added that 25 men and 21 women were now in a stable or satisfactory condition and that health officials were still in the process of compiling the condition of the other 36 people injured in the crash.

Japan's foreign ministry said three Japanese nationals were hurt in the ferry accident, one of whom sustained head injuries and was still in hospital.

City authorities were unable to give further information on the nationalities of the injured, but the route between Hong Kong and the gambling haven of Macau is popular with both international and domestic tourists -- particularly from the Chinese mainland.

Broadcaster RTHK quoted TurboJet spokesman, Wong Man-chung, as saying that the high number of injured was due to passengers not wearing their seatbelts.

Wong added that he was sure the boat had not been speeding and had sustained no major damage.

After the accident the vessel went back to Hong Kong Island's downtown Sheung Wan terminal where a dozen ambulances were waiting to tend to the injured, a government spokesman said.

The safety of Hong Kong's waters was called into question after the fatal October 1, 2012 crash which saw the Lamma IV launch -- carrying more than 120 people -- collide with the high-speed Sea Smooth ferry near Lamma Island.

The launch was carrying employees of the Hong Kong Electric utility and their family members and friends, on a pleasure cruise to watch a fireworks display marking China's national day.

A subsequent inquiry found a "litany of errors" contributed to the accident.

It described how the bow of the Sea Smooth crashed into the main passenger cabin on the Lamma IV, crushing people as water rushed in. The launch partially sank within two minutes.

The two captains have each been charged with 39 counts of manslaughter and are awaiting trial.

The tragedy shocked the Asian financial hub, one of the world's busiest ports, which prides itself on its good safety record.

The marine department has tightened inspections to ensure boats meet safety requirements including adequate lifejackets and watertight fittings.

But family members of those who perished in the disaster have been critical of the government's response to the Lamma disaster.

In August, three people died when a small wooden boat carrying eight people sunk in Hong Kong waters.