President Gloria Macapagal Arroyo was hospitalized Thursday after reporting abdominal pain, but her illness did not appear to be serious, her chief of staff said.

Police in the capital, put on a heightened state of alert earlier in the day due to concerns of possible bomb attacks, were upgraded to full alert after Arroyo fell ill, Manila police chief Vidal Querol said.

Arroyo was taken to St. Luke's medical center after returning from the restaurant to the presidential palace and being examined by a doctor there, chief of staff Mike Defensor said. About a dozen guards were stationed along the corridor of the hospital's fourth floor where she was being treated.

Defensor told reporters Arroyo was being kept overnight as a precaution while she undergoes routine checks.

Her schedule for Friday, which included a Cabinet meeting, was canceled. She was supposed to leave Saturday for a trip to Italy, the Vatican and Spain, and Defensor said a decision on whether to proceed with the trip would be made later.

"She's OK," he said. "The president is resting."

Arroyo had been eating at a restaurant with family members when she reported abdominal pain and an upset stomach, Defensor said.

"There's nothing critical about her situation, nothing to worry," he said. "She's undergoing routine checkups needed so we can be assured there's no complication," he added. "The president has to rest, she has to slow down."

Arroyo, among President Bush's closest allies in the U.S.-led war on terrorism, has been under enormous pressure since she took office in January 2001, grappling with several coup plots and a string of attacks and natural disasters.

Her situation has worsened in the last year as she has survived an impeachment effort over allegations that she rigged the 2004 election. Opponents have threatened to pursue another impeachment attempt when the current one-year ban on filing more than one complaint expires Monday.