Sato, who is running for a third and last term, was ambushed while she was in a convoy heading for her campaign headquarters in Sablayan town, said Lt. Col. Daniel Lucero, Armed Forces spokesman.
No one was hurt in the incident.
Last March 3, Sato, an ally of President Arroyo, was wounded along with three of her companions when the van they were riding in was fired upon in the Mindoro Occidental town of Sta. Cruz.
Sato suffered a gunshot wound in the head. The bullet is still embedded.
The military did not say if the second attack on Sato was related to the first incident.
However, officials have noted that Mindoro island is a known hotbed of New People’s Army (NPA) guerrillas who have ambushed military and police patrols there in the past.
The NPA is extorting money from politicians who are running in the May 10 elections for the right to campaign in their areas of activity. Candidates and campaigners who refuse to pay have been attacked.
A day after the March 3 attack on Sato, the NPA claimed responsibility, accusing the congresswoman of having "blood debts" to the masses. — With AFP report