BBC home affairs producer Daniel De Simone tweeted that the hack was a "serious issue", adding that the press and the public rely on communications from the Metropolitan Police during emergencies such as terror attacks.
"With the incompetent Mayor of London, you will never have safe streets!" he tweeted.
Tweets sent by the hackers made references to Keemstar as well as drill artist Digga D, calling for the rapper to be freed from prison.
The order has caused arguments over government censorship, with police arguing drill music incites gang violence in London. It read: "We are the police..."
Digga D, real name Rhys Herbert, is part of the "1011" drill music group from Ladbroke Grove in West London many of whom are now serving time in jail.
On Friday night, the Twitter account and website of London's Metropolitan Police were targeted by anonymous hackers, who posted a series of unusual messages and emails to subscribers on behalf of the Met's press bureau.
The Metropolitan Police said in a statement the security breach had only affected their MyNewsDesk account, which publishes to the Met's website and Twitter accounts and generates emails.
"The messages have since been deleted, but users were quick to screenshot them".
"While we are still working to establish exactly what happened", it said.
A spokesman for Scotland Yard said the police's own internal infrastructure wasn't hacked; instead, the breach involved a third party site that they use to issue news releases.
The police apologised to its followers for the messages and said, "we are assessing to establish what criminal offences have been committed".
Following Friday's apparent hack Scotland Yard said: "We apologise to our subscribers and followers for the messages they have received".