The fires in the Jordal neighbourhood were quickly extinguished, the Oslo Fire Department said on Twitter.
“We received a message at 2.24am that a car was on fire at a parking lot at Jordal. When we arrived, the fire had also spread to the adjacent car,” Oslo Fire Department spokesman Rune Elstad told Dagbladet.
Elstad said the fires were extinguished and that they posed no danger to nearby residents.
The incident comes as police in both Sweden and Denmark contend with a spate of vehicle fires.
At least 70 cars have been burned out in the southern Swedish city of Malmö since July, while care fires have also been reported in other cities across Sweden, including Stockholm, Gothenburg and Norrköping.
Meanwhile in Copenhagen, three vehicles were torched early on Tuesday in what was the third straight night of car fires.
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Copenhagen Police said a connection to the Swedish fires has not yet been clearly established.
“It is still too early to say anything on the extent to which this could have a connection to the fires that have happened in Sweden,” police spokesman Rasmus Bernt Skovsgaard said on Monday.
As of Tuesday morning, there were no indications that the Oslo fires were connected to the similar incidents in Sweden and Denmark.