By Erik de Castro
ZAMBOANGA CITY, Philippines, Sept 14 (Reuters) - Fighting intensified on Saturday in the southern Philippines between government troops and rogue Muslim separatists, shattering a ceasefire almost immediately as it was to go into effect and leaving many residents running low on supplies.
The army said 53 people had been killed in the fighting, now in its sixth day in the port city of Zamboanga, known as the city of flowers.
Dozens have been wounded and more than 60,000 people displaced, with hundreds of homes razed and a hospital still in flames. Rebels have fired on government positions and seized civilians to use as human shields.
The violence underscores the security challenge potential investors face in the overwhelmingly Roman Catholic country despite a strong second quarter economic performance.
It also called into question a peace deal agreed last October with a larger Muslim rebel group, the Moro Islamic Liberation Front.
Late on Friday, Vice President Jejomar Binay told Reuters he had spoken by telephone to Nur Misuari, leader of a rogue faction of the Moro National Liberation Front (MNLF), and they agreed to a ceasefire and talks to resolve the latest conflict.
Binay announced plans to visit Zamboanga on Mindanao, the Phillipines' southernmost island and theatre of more than four decades of violence.
Heavy fighting broke out after midnight in a coastal village as soldiers retook rebel positions, killing four guerrillas.
Sporadic fighting struck three districts of Zamboanga through the morning and early afternoon. Skirmishes were also reported for the third day on the nearby island of Basilan, with the army saying one of its soldiers had been killed.
Abigail Valte, a presidential spokeswoman, told reporters in Manila, 850 km (510 miles) to the north, that the ceasefire was never implemented. She accused the rebels of launching attacks through the night.
In a radio interview, Defense Secretary Voltaire Gazmin said the vice-president had told him that a ceasefire deal had been clinched, but it had never gone into effect.
"We will only stop firing at them when they stop firing at our troops and the civilians," he said.
Displaced city residents have been given temporary shelter.
But government social workers said some residents trapped in two schools were running out of food as heavy fighting had pinned down relief workers delivering supplies. Banks, shops, offices and some petrol stations remained closed.
Four decades of conflict in the south have killed 120,000 people, displaced two million and stunted growth in the poor but resource-rich area. Muslims account for about 10 percent of the total population of 97 million. (Additional Reporting By Manuel Mogato in MANILA' Editing by Ron Popeski)