A man has been charged after being accused of throwing a device “designed to explode” into a crowd of Invasion Day protesters.

Police evacuated Forrest Place in central Perth on Monday after an object containing ball bearings, screws and liquid was found near a main stage.

A 31-year-old man from the northern Perth suburb of Warwick was quickly arrested and spent the night in custody.

Police on Tuesday confirmed he had been charged with an unlawful act or omission with intent to do harm, and with making or possessing explosives under suspicious circumstances.

Forensic teams searched the man’s home on Monday and the device was examined by the bomb response unit.

“We can say at this time with preliminary testing, the liquid was an explosive liquid, in fact there were multiple liquid compounds,” WA Police Commissioner Col Blanch told Nine Entertainment’s 6PR on Tuesday.

“We will allege that, that device was designed to explode upon impact but for reasons not yet known, it didn’t.

“For whatever reason it hasn’t detonated, but it is explosive compounds and it did contain the ball bearings and the screws and or nails.”

All major capital cities hosted Invasion Day protests while there were opposing right-wing March for Australia rallies in capitals and some regional centres on Australia Day.

January 26 is a day of mourning for many Indigenous people, marking the First Fleet’s 1788 arrival in Australia and the start of British colonisation.

Prime Minister Anthony Albanese on Monday called for national unity after attending a national citizenship ceremony in Canberra.

He welcomed new Australians to their home and said the respect for “common humanity” was what defined the nation.

The accused man was due to face Perth Magistrates Court on Tuesday.

-AAP