At least 15,000 protesters, including two former Philippine presidents, have rallied in Manila, calling for President Gloria Arroyo's resignation over a controversial corruption scandal.

Former presidents Corazon Aquino and Joseph Estrada both joined the rally Friday in Manila's financial district. Soldiers and police were placed on high alert and checkpoints set up around the city.

Ms. Arroyo has already faced three impeachment bids and at least three coup plots since taking office in 2001.

Calls for her resignation have been building again recently as a Senate inquiry investigates allegations into her administration's handling of a multi-million dollar telecommunications deal.

Ms. Arroyo's husband and the country's former election chief have both been accused of accepting bribes and kickbacks in connection with the $330 million deal with a Chinese firm.

The president canceled the contract last year and her husband and the former official deny any wrongdoing.

Some information for this report was provided by AFP, AP and Reuters.