MANILA, July 11 (Reuters) - Philippine security forces ruled out any possibility of riots breaking out due to rising costs of food and fuel as dozens of protesters scuffled on Friday with guards at the headquarters of the country's biggest oil company.

Brigadier-General Romeo Prestoza, head of army intelligence, said authorities were prepared for street protests due to inflation but he did not see a repeat of the violence and rioting in other parts of the world.

"Based on our culture, it's unlikely," Prestoza said after President Gloria Macapagal Arroyo tasked his unit to monitor and provide "timely intelligence assessment of political and security developments related to the oil price issue".

Prestoza said left-wing groups have been using the high cost of food and fuel as a propaganda tool against the government but allayed fears of a breakdown in law and order.

Gasoline prices have risen by about one-third since the start of the year and consumers have been demanding scrapping of a value-added tax, which adds 12 percent to the cost.

On Friday, dozens of students and members of a left-wing activist group pelted the headquarters of Petron Corp with used oil wrapped in small plastic bags during a protest, triggering a scuffle with private security guards.

A team of anti-riot police stepped in to separate the two groups. There were no arrests and no injuries reported.

"In the coming weeks, there will be civil unrest," Andrew Zarate, a spokesman for the left-wing activist group Anakbayan, told reporters. "The crisis will push people to come out, protest, make noise and express their anger against the government." (Reporting by Marnette Federis; Writing by Manny Mogato; Editing by Raju Gopalakrishnan)

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