The Foreign Office also announced new efforts to stop UK businesses working with Myanmar’s military and measures to ensure aid is not diverted to the junta.
Foreign Secretary Dominic Raab said: “The UK condemns the military coup and the arbitrary detention of Aung San Suu Kyi and other political figures.
“We, alongside our international allies will hold the Myanmar military to account for their violations of human rights and pursue justice for the Myanmar people.”
The sanctions will be imposed on defence minister General Mya Tun Oo, home affairs minister Lt General Soe Htut and deputy home affairs minister Lt General Than Hlaing.
UK officials said Canada was taking similar action, and pledged that aid would still reach “the poorest and most vulnerable in Myanmar.”
Even before the coup Britain had imposed sanctions on 16 other members of Myanmar’s military for human rights violations.
The Myanmar military seized power on February 1 and detained national leader Aung San Suu Kyi and other pro-democracy figures.
The junta said the takeover was necessary because Suu Kai’s government had failed to investigate fraud claims in elections her party won in a landslide; the election commission has dismissed those claims.
Since the coup, the junta has ratcheted up the pressure on protesters resisting the takeover, including violently breaking up some demonstrations and blocking internet access
The UK is the ex-colonial ruler of Burma, as Myanmar was formerly known. Prime Minister Boris Johnson previously condemned the coup and described the imprisonment of Ms Suu Kyi as “unlawful”.
Additional reporting by agencies