Some more than 20,000 pairs of counterfeit Christian Louboutin shoes have been seized by the US Customs and Border Protection (CBP).

The CBP said it seized five shipments of shoes arriving from China at the Los Angeles/Long Beach seaport, containing 20,457 pairs of women's footwear. The shoes have a retail value of US$18m and a domestic value of $57,490.

"This seizure illustrates the outstanding level of commodity expertise and vigilance of CBP import specialists and officers at our nation's largest seaport. CBP maintains an aggressive and proactive posture on intercepting shipments containing counterfeit and pirated items," said CBP director of field operations in Los Angeles Todd Owen.

During the 2011 fiscal year, there were 1,020 trade seizures with a domestic value exceeding $37m at the Los Angeles/Long Beach seaport complex, an 18% increase on 2010.