United Nations sanctions on Iran over its nuclear program have been reimposed.

Here's what to know about Iran's nuclear sites, "snapback" sanctions and other issues raising tensions between Iran and the West:

WHAT IS 'SNAPBACK' AND HOW DOES IT WORK?

The "snapback" process, as it is called by the diplomats who negotiated it into Iran's 2015 nuclear deal with world powers, is designed to be veto-proof at the UN Security Council and took effect 30 days after parties to the deal told the Security Council that Iran was not complying

The UN again froze Iranian assets abroad, halted arms deals with Tehran and penalised any development of Iran's ballistic missile program, among other measures

China has remained a major buyer of Iranian crude oil, something that could be affected if "snapback"

See Full Page