The shopping sales day is among Amazon's busiest all year.

An international coalition of unions, equality and environmental groups called "Make Amazon Pay" is staging a day of action, demanding concessions.

Meanwhile, the Extinction Rebellion environmental group has targeted Amazon depots in the UK, blocking entrances and access roads.

The group has blocked Amazon centres in Tilbury, Essex, and at Avon mouth near Bristol, according to reporters on the scene. It says it is also staging action in Manchester, Newcastle, and abroad in Germany and Netherlands.

In all, it says it has blockaded 15 centres - 13 of which are in the UK.

"Black Friday epitomises an obsession with over-consumption that is not consistent with a liveable planet," the group said.

According to BBC Amazon issued a prepared statement in advance of the protests about the wider Make Amazon Pay movement.

"These groups represent a variety of interests, and while we are not perfect in any area, if you objectively look at what Amazon is doing in each one of these areas you'll see that we do take our role and our impact very seriously," it said.