The UK summoned Iran's ambassador to London on Tuesday because of Tehran's role in rising tensions across the Middle East, according to a statement.
Seyed Ali Mousavi "was summoned in response to Iran's role in recent events across the Middle East," it said.
The decision follows "escalatory behaviour by the Iranian regime which has attempted to draw the region into a wider conflict-attacking countries who had not attacked them."
London described the situation as posing direct risks to regional stability and British nationals.
"This presents a clear threat to the security of the region and to the hundreds of thousands of British citizens in the region," said the statement, stressing that "Iran must be held accountable for its actions."
The UK underlined that "protecting national security and the lives of British nationals remains our top priority."
Joint US-Israeli attacks on Iran launched Saturday killed several senior Iranian officials, including Supreme Leader Ayatollah Ali Khamenei.
Tehran has retaliated with strikes targeting Gulf countries and US military assets in the region.
