A group calling themselves "Topple the Tyrants" have occupied the £10 million house in Hampstead Garden Suburb in north London.
Members of the group have vowed to remain in place until the property's assets are returned to the Libyan people, according to the BBC.
Spokesman Montgomery Jones said: "We will stay here until we can be sure the property will be returned to its rightful owners.
"The police came to look around, then went away. The house isn't occupied at the moment but there are things to sit on."
The group said the property was managed by the Gaddafi family through a holding company registered in the British Virgin Islands.
In a statement, it said: "We didn't trust the British government to properly seize the Gaddafi regime's corrupt assets, so we took matters into our own hands.
"In the meantime, we want to welcome refugees from the conflict in Libya and those fleeing tyranny and oppression across the world.
"We stand in solidarity with the Libyan people."
A Scotland Yard spokesman said: "Police were called to an address in Hampstead Garden Suburb at approximately 12.50 on Wednesday to reports of unknown people entering the premises. At this time it is being treated as a civil matter."
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