Thousands of protesters have taken part in a rally in the Philippine capital, Manila, to demand the resignation of President Gloria Arroyo.
Protests over alleged corruption have been rumbling on for weeks
Security was tight for the rally in the Makati financial district, with troops and armoured vehicles on stand by.
The protesters want Ms Arroyo to step down over claims her husband and an ally sought kickbacks linked to a government deal with a Chinese firm.
Both men deny the allegations and the deal has been cancelled.
In Makati, crowds of marchers carried banners urging the president to resign, despite warnings from the military of possible trouble at the rally.
On Thursday, army chiefs said communist rebels could try to infiltrate the crowd - a warning opposition leaders dismissed as justification for increased security.
The military also said on Thursday that it had uncovered details of a plot by al-Qaeda-linked militants to assassinate Ms Arroyo, but said this did not appear to be related to the rally.
The corruption row - relating to a multi-million dollar deal for a government broadband network - has been rumbling on for several months.
Ms Arroyo cancelled the deal because of the corruption allegations, which are now being investigated by the Senate.
Speaking earlier in the day to business leaders, the president promised a "thorough and transparent" probe.
"We do not want to tolerate corruption," she said.
"There is no room in the development of our country for wasting money on corruption when so much remains to be done to invest in the nation."