Two were police officers.
Tamaulipas state security spokeswoman Ivon Melendez said today that nine suspected criminals were killed after attacking state police in the border town of Rio Bravo on Saturday afternoon.
Rio Bravo lies in territory controlled by the Gulf drug cartel.
Also on Saturday, two off-duty state police officers were killed in the border city of Nuevo Laredo. Melendez says they were on their way to Laredo, Texas, to shop when gunmen in two vehicles opened fire. One officer survived the attack.
The Zetas cartel controls Nuevo Laredo.