Switzerland announced tougher sanctions against Iran on Thursday but refused to implement an outright ban on oil imports "for policy reasons".

The sanctions -- which come into force on July 6th -- are in line with measures imposed on Iran by the European Union.

They include a ban on the supply of petrochemical equipment and diamonds to Tehran, the Federal Department of Economic Affairs (FDEA) said in a statement.

All imports of crude oil and related products from Iran, which have been banned in the EU since July 1st but not in Switzerland, must nonetheless be declared to the State Secretariat for Economic Affairs, the FDEA said.

"For foreign policy reasons, transactions involving Iranian oil and petrochemical products have not been prohibited as in the EU, but they are instead subject to a declaration requirement."

Switzerland has imported no crude oil from Iran since 2006, according to the FDEA, which said that "further measures" may be taken against Tehran "based on reports received".

Financial measures were also imposed against 78 Iranians accused of serious human rights violations, the FDEA said.