UPS and other carriers raised their shipping rates in January, much to the chagrin of U.S. e-commerce retailers. Now, some industry observers believe Amazon may be the cause of the price hikes.

A series of general rate increases on the Asia-North Europe trade have gone into effect as container shipping lines once again attempt to force freight rates up to break-even levels, amid warnings from shippers and analysts that pricing volatility is set to continue - and possibly worsen.