The UN took that step over the weekend after Western powers triggered the so-called "snapback" mechanism under the 2015 nuclear accord.

The sanctions reintroduced by the 27-nation bloc include UN measures barring dealing with Tehran's nuclear and ballistic missile activities.

But they also range broader to encompass financial measures, including freezing assets of Iran's central bank.

Tehran has condemned as "unjustifiable" the reinstatement of the UN sanctions.

Despite the reimposition, Western leaders stressed channels for dialogue remained open.

Kaja Kallas, the European Union's top diplomat, said on Sunday the reimposition of sanctions "must not be the end of diplomacy".