At least 17 people have died in a series of shootouts that started over the weekend in Tampico, a city in the northeastern Mexican state of Tamaulipas, and continued into this week, the Tamaulipas Coordination Group, or GCT, said.

The shootouts began around 3:00 p.m. Saturday in the neighboring city of Madero and spilled over into the streets of the port city of Tampico.

"Two unidentified armed civilians killed two men and a woman. Ten minutes later, in the Las Violetas de Tampico section, the dead body of an unidentified man was found with a gunshot wound in the head," the GCT, a joint federal and state agency, said.

At least 10 people had been killed by midnight Saturday in different neighborhoods in Tampico, the GCT said.

Three men, all suspected of being members of criminal organizations, were gunned down in the port city on Monday, the GCT said.

Two universities in Tampico cancelled classes on Monday, but the public schools remained open and officials reported no problems.

Residents posted messages all day Monday on social-networking sites about gunfire, the presence of gunmen in different neighborhoods and the torching of businesses and vehicles in Tampico.

The Gulf and Los Zetas drug cartels have been fighting for control of Tamaulipas and smuggling routes into the United States for years.

The recent arrests of two Gulf cartel bosses triggered the shootouts, with different factions of the gang battling for control of various areas, security officials told Efe on condition of anonymity.

Shootouts have been reported in a number of cities across Tamaulipas since last Thursday, but officials have not provided figures on the number of people killed. EFE