PERTH (AFP) - An explosion in an electrical transformer room at a shopping centre in the west Australian city of Perth has left two men dead and two others badly burnt, authorities said on Tuesday.

Western Australia police said a 30-year-old man died at the scene while three other men were taken to Royal Perth Hospital with serious injuries.

"Tragically, one of the three men taken to hospital has since passed away," police said in a statement.

Witnesses spoke of their horror at seeing the men, thought to be working in an area near the electrical transformer, come running out after the morning explosion.

"I came driving in and saw three people come running out... they were on fire," Mr Jonathan McDonagh told Australian Associated Press, saying he tried to help the injured, taking off his shirt and using it to put out the flames.

"I had the radio on and didn't hear the bang, but I saw a puff of smoke.

"One fella was dead on the ground. I saw another moving around, obviously not OK. I gave him a good helping hand, as much as I could.

"They were really burnt badly."

Another witness, Mr Harry Barugh, said he thought at first a car had exploded.

"But it was a lot worse than that, it was the worst sight I have ever seen in my entire life," he told the Australian Broadcasting Corporation.

"It was just 'whoosh' and then there were these guys just coming out and hitting the deck and then ripping their gear off."

A woman who suffered smoke inhalation was also taken to hospital while several other people were treated for shock and smoke inhalation at the scene at the Galleria shopping centre in the Perth suburb of Morely.

Fire and emergency services cordoned off the area with investigations into what caused the blast under way.

"We believe that they possibly were workers who were working within that transformer area of the shopping centre," police inspector Rob Harrison said.