The U.S. State Department has renewed a travel advisory for U.S. citizens crossing into Mexico, saying there is an "unacceptable" level of violence in the border region.

Officials say the advisory issued Tuesday, was necessary due to the more than 100 violent deaths that have occurred since June and the killing of 18 policemen in the border town of Nuevo Laredo this year.

The advisory acknowledges the Mexican government's efforts to address the continuing violence, but says Mexico City still needs to do much more to tackle the problem along the 3100 kilometer border.

Hours after the State Department announcement, the Mexican government said it has made a series of efforts to stop the violence and is searching for long-term solutions to the problem.

The U.S. announcement updates a similar notice issued in April.

Some information for this report provided by AP and Reuters.