Agent provocateur

"This agent-provocateur business is quite foreign to British justice."

Source: wiktionary

I was told afterwards—quite possibly it was true—that agents provocateurs were touching off masses of explosive in order to increase the general noise and panic.

Source: wiktionary

Suspecting that the man was an agent provocateur sent by the Prince, Pottinger told him that regrettably he had neither the knowledge nor the authority to instruct him in this or any other religion.

Source: wiktionary

The criminalisation of protest has been aided by the director of public prosecution's recent guidelines on prosecuting protesters, which fail to account for the role of the police in prompting violence at demonstrations through tactics such as kettling, the use of batons, agents provocateurs and undercover policing.

Source: wiktionary