Hong Kong has thrived as Asia's throbbing transport hub, but a deadly ferry accident on the busy National Day holiday has raised questions about safety on the city's frenetic harbour.

A total of 37 people were killed and scores injured when a passenger ferry collided near Lamma island with a vessel carrying company employees on a pleasure cruise to watch holiday fireworks on Monday evening.

It was the deadliest maritime accident in the territory since 1971, when 88 people were killed as a Hong Kong-Macau ferry sank during a typhoon.

The Asian financial centre is one of the world's busiest ports, with more than 425,000 vessels arriving and departing in 2010, according to official figures.

On any given day, scores of cargo ships can be seen moored in clusters around the port, and at night the horns of passing leviathan container vessels echo towards the city.

But fatal accidents are rare on Victoria Harbour's crowded waters, despite high-speed hydrofoils vying for space with red-sailed tourist junks, luxury private yachts and the 100-year-old Star Ferries that connect Hong Kong to Kowloon.

Researchers say that while it remains one of the world's safest ports, increased vessel traffic and risks associated with land reclamation works along the harbour front call for urgent government attention.

"People will start querying whether Hong Kong's marine traffic management has been kept up to pace," Albert Lai, the founding chairman of think-tank The Professional Commons and a trained civil engineer told AFP.

"It certainly affects Hong Kong's international reputation as a shipping hub," he added, calling for a review of marine traffic systems in the former British colony.

Despite the importance of marine transport to the city's seven million population, passengers said the ferry crew involved in Monday night's incident appeared to have no training on how to respond to such an emergency.

"The crew was terrible, useless. They just stood around as we were putting the life jackets on... The crew didn't seem to know what was going on," Clare Kirkman, a 43-year-old Briton who has lived on Lamma for 10 years, told AFP on Tuesday.

"The worst thing is that they seemed more concerned with getting the life jacket from us when we got to the pier. It was a good 10 or 15 minutes until we got to the ferry pier but I didn't see any ambulances or police.

"It was a quiet ferry but it was concerning the ferry people weren't more helpful. God forbid if it had been a school ferry."

Residents of Lamma -- a sleepy, car-free island to the east of Hong Kong which is inundated with thousands of day trippers on weekends -- expressed anger at the number of ferries put on to cater for the holiday crowds.

"I have seen ferries back-to-back but this was just ridiculous. I don't think they should be able to bring so many people to the island," said Kay Travers, a Lamma resident of 18 years.

Officials said the incident was still under investigation and have refused to speculate about the cause of the accident. Six people were arrested, three crew from each vessel, said the territory's security chief Lai Tung-kwok.

All of the dead and most of the injured were aboard the party boat which was taking staff and families of power company Hong Kong Electric on a cruise to watch the fireworks.

The single-hulled vessel with a capacity of 200 people sank within minutes of the impact, leaving only its blue bow poking above the choppy waves.

Shipping experts say that given the intensity of traffic, the rate of fatal incidents in Hong Kong is low.

But Lai pointed out that water traffic had risen significantly in recent years as soaring accommodation prices on Hong Kong drove more and more people to live on outlying islands such as Lamma.

He said the hundreds of hectares (acres) of land reclaimed along Victoria Harbour over the past decade made journeys on small boats more perilous, as they were pushed into lanes used by powerful high-speed ferries.

"The harbour has become smaller, making the waves generated by ferries crossing the harbour higher and making the water more choppy," he said.

Asked if the accident damaged the port's reputation, Hong Kong's chief executive Leung Chun-ying told AFP: "This is definitely an isolated incident. The marine territory of Hong Kong is safe."