Seventeen people were arrested in anti-austerity protests close to Downing Street in central London, the Metropolitan Police said.
In the wake of the Conservative's victory in the general election, police clashed with a "minority" of protesters, demonstrating against the government policy of cutting government spending.
Ch Supt Gerry Campbell said that though the majority of protesters behaved well, a "small minority" were intent on causing disorder.
Hundreds gathered outside the Conservative Party headquarters in Whitehall before heading to Downing Street.
The Met estimated that approximately 100 protestors had gather, but photographs taken in the area at the time suggest that approximately 1,000 had attended.
There were claims on Twitter that up to 500,000 protestors had marched on Downing Street.
Some protesters complained of police violence and alleged that demonstrators had been "kettled" in Parliament Square, a police controversial police tactic in which protesters are detained in a certain area.
In clashes with protesters, who hurled traffic cones and smoke bombs, several officers were injured.
Arrests were made for offences including violent disorder and assault on a police officer, the Met said.
The protest was arranged at short notice over social media, the Guardian reported.
A protest near the Downing Street area had been arranged over social media prior to the general election.
It was in reaction to a Times' opinion column which called on Prime Minister David Cameron to remain in Downing Street in the event the Conservatives lost the election and a new coalition would have to be formed.
A police investigation is underway, after a war memorial was defaced with anti-Tory graffiti during the protests.
The Women's War Memorial in Whitehall was daubed with "Tory Scum", a short distance from where a VE Day memorial concert had been played on Saturday.
"We have launched an investigation into criminal damage to the Women in World War Two Memorial. This is particularly abhorrent considering we are celebrating the 70th anniversary of VE Day," he said.
In Cardiff, singer Charlotte Church was among those who took part in a peaceful anti-government cuts march.