MANILA, Philippines?With the official opening of the campaign period for national positions, police have beefed up security at various places in Quezon City, including the National Printing Office where ballots for the May 10 elections are being printed, police said.

``We have reinforced our presence in areas in the city which are considered as potential place for negative incidents to prevent any negative incidents,'' Chief Supt. Elmo San Diego told the Inquirer as he inspected police deployment in several parts of the city on Monday night.

He was accompanied by Quezon City Comelec officer Ronald Allan Sinco to personally see some of the checkpoints.

San Diego said that a team of policemen has been assigned to the NPO office on EDSA to beef up security around the facility.

?The NPO has its own security inside, but we added more policemen to conduct roving patrols around the perimeter just to be sure no one would try any foolishness,'' San Diego said.

He noted that the NPO has started printing election ballots.

No reports of threats have been received, he said, adding, ?We just want to be ready and proactive.''

San Diego said soldiers from the Philippine Army were also deployed at various checkpoints as support personnel.

?We believed that we need to strengthen our checkpoints, not only for possible untoward incidents, but also because the city is big [strategically] located where candidates could meet,'' he said.