Thousands of white-clad people marched silently Sunday to protest a surge of drug-related violence in a Mexican city across from Texas where the No. 2 police officer was shot dead.

The crowd of several thousand students, church leaders, businessmen and politicians walked for about four miles (six kilometers) across Ciudad Juarez to a park near a border crossing, breaking the silence in a burst of speeches, dancing and singing.

More than 200 people have been killed so far this year in Ciudad Juarez. The city of 1.3 million across the border from El Paso, Texas, is home base for the powerful Juarez drug cartel.

The assassination of police director Juan Antonio Roman Garcia on Saturday came despite the deployment of more than 2,500 soldiers and federal police to the city and surrounding Chihuahua state in March.

"We need to unite against this," said Julian Ochoa, an architecture student at the march. "I hope we achieve something."

An increase in drug-related homicides, shootouts, kidnappings and car thefts near the border prompted U.S. State Department to warn Americans last month of rising violence in the region, though it stopped short of advising against travel here.

On Saturday, police arrested six suspected gang members after a gunfight in the northern state of Sinaloa. One of the six, Alfonso Gutierrez Loera, 25, identified himself as a cousin of suspected Sinaloa cartel chief Joaquin Guzman, according the Public Safety Department. Gutierrez Loera and another suspect were wounded in the shootout.