Britain introduced a raft of new sanctions Thursday targeting Iran's "decision makers and those doing its bidding," including Hamas and other Palestinian groups.
The travel bans and asset freezes were coordinated with Washington and aim to disrupt what London calls Tehran's "hostile activities in the UK and around the world".
The targeted individuals include Esmail Qaani, the leader of the Islamic Revolutionary Guard Corps (IRGC) Quds Force, and seven other linked to Iran's allies Hamas and Palestinian Islamic Jihad.
Britain has long designated both Palestinian groups as terrorist organisations.
London also placed sanctions on the Palestinian branch of the IRGC.
The sanctions strengthened export restrictions on drone components, and introduced new powers to impose transport sanctions on ships involved in contravening existing sanctions or controlled by sanctioned individuals.
"The behaviour of the Iranian regime poses an unacceptable threat to the UK and our partners," Foreign Secretary David Cameron said.
"It continues to threaten people on UK soil and uses its influence to destabilise the Middle East through support to armed groups, including Hamas and Palestinian Islamic Jihad."
Washington, which had already sanctioned most of those targeted by London, announced it was joining Britain in sanctioning IRGC official Majid Zaree, whom it said supported Hamas and the Lebanon-based militant group Hezbollah.
Deputy Secretary of the US Treasury Wally Adeyemo said the joint action "will be instrumental in taking action against Iranian support to Hamas and other regional proxy groups that fan conflict and contribute to widespread suffering".
London accuses Iran of human rights abuses as well as stepping up efforts to kill or kidnap perceived enemies of its regime, including in Britain.
It says the Iranian intelligence services have developed close relationships with organised criminal gangs in the UK and across Europe to help target opponents.
The latest measures add to ones already imposed over Tehran's hardline response to protests that have rocked the Islamic republic since the September 2022 death in custody of Iranian-Kurdish woman Mahsa Amini.
The 22-year-old had been arrested for an alleged breach of strict dress rules for women.
The UK has targeted more than 350 Iranian individuals and organisations, including other leading IRGC commanders and Tehran's prosecutor general.
The US and the European Union have also toughened their own sanctions.