Two die in plane crash watched by Australia Day crowd Published duration 27 January 2017

image copyright Getty Images image caption The plane crashed into Swan River in Perth, Western Australia

Two people have died in a light plane crash in Perth as a crowd celebrating Australia Day watched on.

The Grumman G-73 "Mallard" flying boat nosedived into Swan River in Western Australia's capital just after 17:00 local time on Thursday.

Pilot Peter Lynch, 52, and his girlfriend Endah Cakrawati, 30, were the sole occupants, police said.

An annual fireworks celebration, expected to draw 300,000 people to the river, was immediately cancelled.

Western Australia Police acting commissioner Stephen Brown said the cause of the crash was being investigated.

"I was actually standing on the Perth foreshore doing a live cross to one of the TV channels when the tragic events unfolded in the sky above me," he said on Friday.

"It clearly had broken at least in two significant parts, and was sinking very quickly."

image copyright Great Eastern Fly-In image caption Peter Lynch was a "well-loved" member of the aviation community

Mr Lynch was a father of three, according to Fortescue Metals Group, where he worked as a mining executive.

Ms Cakrawati was a public relations manager for Cokal, an Australian-listed coal company.

"Peter was a great mate and all of us at Fortescue convey our deepest condolences to his family, including his three children, and to Endah's family," Fortescue chief Nev Power said in a statement.

Mr Lynch was described as "well-loved and respected" by the Great Eastern Fly-In, an aviation community.

Crowd shocked

Witness Lloyd Douglas, who was on a nearby boat, said the plane appeared to stall as it turned towards the city.

"As he banked left he seemed to go further to the left ... and lose forward momentum and lost altitude fairly quickly," he told the Australian Broadcasting Corp

Another onlooker, Craig Newill, said the accident shocked his family.

"[The] wings were pointing to the sky and to the water and we thought 'this is not good', then we saw it break into two pieces," he told Perth Now

image copyright EPA image caption Fireworks celebrations were cancelled after the crash

Mr Brown told reporters it was fortunate the plane did not hit the crowd.

"For reasons yet unknown, it's entered the waterway, thankfully without injuring anyone else on the ground or any other people who are here the event," he said.

Perth Lord Mayor Lisa Scaffidi said the fireworks were cancelled out of respect to the victims and to "conserve the integrity of the [crash] site".

The plane remained in the river overnight.