Apple has issued a voluntary recall of millions of its two-prong AC wall plugs after incidents of them breaking and causing electric shocks.

Apple said it knew of 12 such incidents and asked customers to stop using them.

The plugs came with Macs and other iOS devices sold in Continental Europe and five other countries around the world between 2003 and 2015 and were included in the Apple World Travel Adapter kit.

Apple said customer safety was its "top priority".

The recall relates to plugs for: Continental Europe, Argentina, Brazil, Australia, New Zealand and South Korea.

It does not affect plugs for: US, UK, China, Japan and Canada.

Affected users can exchange their plug at their local Apple store or request a replacement via the website.

Last year, Apple urged owners of one of its Beats loudspeaker systems to stop using the kit because it posed a fire risk.

In 2014, the company offered a free exchange for one model of USB iPhone chargers sold in Europe between 2009 and 2012, after a few cases of overheating.