The European Commission has signed an agreement with four major online retailers to combat the listing of dangerous products on Europe's online shopping sites.

Dangerous content, as defined by the Commission, includes anything from incitement to hatred and violence to child sexual abuse material, unsafe products and products infringing copyright.

AliExpress, Amazon , eBay and Rakuten-France <4755.T> agreed to remove dangerous product listings within two days of being notified by authorities and respond to customer notifications within five days.

The Commission said 20 percent of sales in Europe were made online in 2016, increasing the prevalence of dangerous product listings.

"E-commerce has opened up new possibilities for consumers, offering them more choice at lower prices. Consumers should be just as safe when they buy online, as when they buy in a shop," Commissioner Vera Jourova, who looks after consumer issues, said.

The companies also agreed to train sellers to comply with EU safety law and utilise the EU's Rapid Alert System to be proactive in the monitoring and preventing of unsafe product listings.