The boy and girl,aged four and six,were seen in the water at Burswood near Perth Stadium about 5.25pm on Sunday.
Police said two children were pulled from the Swan River but could not be revived.Nine News
They were pulled from the river by members of the public,but were unresponsive by the time paramedics arrived on the scene,WA Police said.
Both children were given CPR and taken to Perth Children’s Hospital but could not be revived.
Police said the children were from two separate families but were known to each other.
Eight ambulances responded and police cordoned off the area.
The incident happened near a children’s playground as revellers gathered for New Year’s Eve celebrations.
One bystander told Nine News that he had seen a man jump into the river and pull the children out.
A woman who said she was a nurse started to perform CPR,he said.
Another onlooker praised the efforts of multiple bystanders and first responders who tried to save the children.
“Our thoughts and prayers are with the family and those people that were involved,” acting commander Mark Longman said on Monday.
“We can only begin to imagine the trauma and suffering that those families will be experiencing at this time and whilst it’s early days,police will be providing significant support to those families including specialist family liaison officers to help them through the process of dealing with this tragedy.
“I would also express my thoughts and condolences to the members of the public who were there at the time and may have witnessed what is a tragic and extremely sad situation and the impact it will have on everyone.”
A report will be prepared for the coroner.
AAP