Russia has adopted new United Nations economic sanctions on Iran aimed at getting Tehran to suspend its nuclear enrichment activities.

The Kremlin announced Thursday that former President Vladimir Putin signed the sanctions into law earlier this week, just before stepping down to be replaced by Dmitri Medvedev.

The U.N. Security Council imposed the sanctions on Iran in early March. They tighten existing sanctions on trade, and on the travel and assets of people involved in Tehran's nuclear and missile programs. They also call for vigilance over banks in Iran.

This is the third set of sanctions the Security Council has imposed on Iran for its refusal to halt uranium enrichment, a process that can be used to make nuclear weapons.

The United States and its Western allies accuse Iran of working to build a nuclear weapon. Iran says its atomic program is for peaceful purposes.

Russia has been helping Iran build its first nuclear power plant. It is located in southwestern Iran on the Gulf Coast.