A female Metropolitan Police officer is being investigated after being filmed chanting "Free Palestine" during a demonstration.
Clips of the officer were posted on social media which led to some users questioning whether she should have been expressing political views while on duty.
The force said its internal Directorate of Professional Standards is investigating what happened.
Crowds of people marched through London on Saturday to the gates of the Israeli embassy, while protests took place in other cities across the UK and Ireland in solidarity with the people of Palestine.
A spokesman said: "We are aware of a video that has been posted on social media which shows an officer joining in with chanting while on duty at a demonstration.
"While officers are encouraged to positively engage with those attending demonstrations, they know they are not to actively participate or adopt political positions. This is vital to ensuring the public have confidence in our officers.
"The Directorate of Professional Standards has been informed and are investigating the full circumstances of this incident and to determine what further action is appropriate."
Thousands of Palestinians have been forced to flee their homes after a week of sustained conflict.
Since last Monday night, the Palestinian militant group Hamas has fired hundreds of rockets into Israel, whose military responded by barraging the Gaza Strip with tank fire and airstrikes.
A post on the Twitter account @MPSEvents in response to the footage stressed that officers must remain "impartial" while on duty at protests.
It said: "We police hundreds of public events and protests in London every year and officers must remain independent and impartial in carrying out their duties."
The incident echoes controversy that erupted last summer when some officers were seen taking the knee in a gesture of solidarity with Black Lives Matter protesters.
Commissioner Dame Cressida Dick said afterwards that officers should not take such action while on duty.