The Metropolitan Police said on Saturday that all roads close to the Palace of Westminster had been sealed off after officers saw the vehicle in the area.
The police said officers had closed roads at Victoria Embankment next to the River Thames and by Parliament Square and close to New Scotland Yard, where The Met headquarters is located.
Later reports suggested the vehicle had been deemed non-suspicious and roads re-opened. Reports said heavy police presence could be seen in central London during the lookdown.
The lockdown comes amid increased sense if insecurity at crowded places in London and other parts of the UK after authorities reported the arrival of bomb packages earlier this week.
The Met received reports of a suspicious package in east of the city on Wednesday, a day after white postal bags containing small parcel bombs had been sent to London’s Heathrow and City Airport, and its busiest train station Waterloo.
Many fear the parcel bombs, also received in Scotland, are being sent by separatists in Northern Ireland, a British province with a history of bloody violence that left thousands killed until late 1990s.
Irish separatists have launched at least three major attacks, a bombing and two shootings, in Northern Ireland this year. Such attacks could intensify with a disorderly British withdrawal from the European Union at the end of March, as it could lead to a hard border between the two Irelands.
Places like London’s Westminster Bridge have been the scene of terrorist attacks over the past years, including one in 2017, a year during which a total of 36 people were killed in five terror attacks and prompting government to raise terrorism alert to its second highest level.