The Los Angeles Times says the "concertina" wire has been added to the existing fence separating San Diego from Tijuana, Mexico. The move marks a major shift for the Border Patrol, which in the past has shied away from using such fencing because of the negative connotations its appearance creates.

Border officials told the newspaper that escalating violence from human smugglers has created the need for the new fortifications, specifically from Colonia Libertad, a notorious Tijuana smuggling enclave. U.S. officials contend the razor wire has proven to be effective in controlling the smugglers.

However, critics say the wire is inhumane and could severely injure illegal immigrants attempting to enter the United States.

The southern California area has frequently seen violence between rock-throwing Mexican youths and Border Patrol officers, who respond by firing tear gas and pepper spray to disperse the attackers. Despite attempts to cooperate with Mexican authorities, the attacks are continuing, the Times reported.