Two Scottish tourists have been charged after a tip-off about suspicious activity at an Airbnb ultimately led police to allegedly uncover 105kg of ketamine.

Neighbours had noticed unusual behaviour at the short-term stay on Hampden Road in Artarmon, on Sydney's lower north shore, on June 26.

NSW Police were alerted and officers allegedly discovered 2kg of ketamine powder inside abandoned luggage.

Commercial scales, disposable gloves, clear resealable bags with crystallised residue were also allegedly found at the premises.

An investigation then led detectives to a hotel in North Sydney three days later.

A 30-year-old Scottish man and 23-year-old Scottish woman were arrested following a raid on one of the rooms.

Police allegedly uncovered $2,000 in cash, six mobile phones and handwritten drug ledgers.

Inside a rented vehicle in the hotel carpark, police allegedly found 105kg of ketamine, worth $11million, hiding in shopping bags and plastic totes.

Detective Acting Inspector Alison Dixon praised her officers.

'My team acted swiftly... disrupting their alleged illegal activity,' she told news.com.au. 

The two Scottish tourists allegedly flew into Australia from the UK and used the short-term stays to fly under the radar of authorities. 

'We will allege that the couple travelled from the UK for the sole purpose of taking part in illegal drug supply,' Det Act Insp Dixon said. 

She encouraged Australians to report any suspicious activity at Airbnbs.

'We have seen this before in short stays and encourage property owners to be wary,' Det Act Insp Dixon said.

'Stuff out of the ordinary that doesn't look right... if it doesn't look right, it probably isn't.' 

The man and woman were charged with supplying a commercial quantity of prohibited drugs.

They were refused bail at Manly Local Court. 

The pair will appear at Downing Centre Local Court in August.