A huge protest promised by Philippine opposition groups is expected to be seen as a barometer of President Gloria Macapagal Arroyo's chances of survival.
Police said up to 30,000 people, most of them young men, were converging at a
Demonstrators at the huge protest rally demanding the resignation of Philippine President Gloria Macapagal Arroyo
major intersection along Ayala Avenue, an eight-lane artery through Manila's business district.
"Oust Gloria now," the crowd chanted. "Gloria is a thief."
Analysts had said anything over 20,000 marchers may signal rising public rage against Arroyo and counter her new-found resilience after a former president came to her rescue last week and the Catholic Church did not join calls that she step down.
The month-old crisis has kept financial markets nervous and raised fears that a protracted political battle will paralyse Arroyo's reforms aimed at raising revenues and cutting debt.
The president has defied demands for her resignation over allegations of vote-rigging in last year's election and graft by members of her family, saying to quit now would condemn future governments to endless turmoil.
"She will not make a decision based on the number of people in the streets," Rigoberto Tiglao, head of the presidential staff, told journalists.
He scoffed at reports that Arroyo's foes could muster up to 1 million people in protests set to run until Sunday.
Some opposition groups complained that police were blocking caravans of supporters coming from the provinces.
Police said the final size of the crowd would depend on the weather and the scheduled appearance of actress Susan Roces, the widow of Fernando Poe Jr, a movie star who died in December after losing the May 2004 presidential election to Arroyo.
Organisers said the protesters would swell over the day to 40,000 or 50,000 - a big step up from recent rallies of around 8,000 but far from the hundreds of thousands who took to the streets of Manila to overthrow presidents in 1986 and 2001.
But analysts said Arroyo, a US-trained economist and the daughter of a late president, would not be under immediate threat unless protests grew larger and more frequent.
There were no signs yet that Arroyo's traditional foes - leftist, student and farmers' groups combined with supporters of deposed president Joseph Estrada - were being joined by the middle class, whose presence was crucial in past uprisings.