MANILA, Aug 13 (AFP) - The Philippines on Saturday ordered a heightened alert at air and sea ports in Manila and key southern cities after bomb attacks last week and reports of possible suicide attacks from Indonesian militants.

The capital Manila, the central city of Cebu and the southern hubs of Davao and Zamboanga, which could be likely targets, are under particular watch, said Eduardo Ermita, President Gloria Arroyo’s chief aide and head of the country’s anti-terrorist task force.

Malls, theaters, bus stations and other public installations in these cities have been briefed about possible attacks, Ermita said.

"We have ordered the Coast Guard, the Aviation Security Command, the police and the armed forces to closely watch characters, groups where these terrorist threats are coming from," Ermita said in a radio interview. "We have stepped up our security."

The security clampdown came three days after suspected Abu Sayyaf militants set off two bombs in Zamboanga city, wounding 26.

"Our intelligence units are monitoring very, very closely the movement of terrorist elements," Ermita told AFP, declining to give specific details citing security concerns.

"We have forewarned everyone concerned about the efforts of the terrorists, particularly the Abu Sayyaf and JI (Jemaah Islamiyah) to stage attacks" he said. "Our aim is the prevention of possible attacks in places where people converge."

He said intelligence units in the southern island of Mindanao were tracking down 10 Indonesian JI militants reportedly being aided by the Abu Sayyaf in scouting targets.

Foreign governments, including neighbors Malaysia and Indonesia, could also be asked to help in providing information, Ermita said.

Ermita’s deputy, National Security Adviser Norberto Gonzales, last week said that up to 10 JI members were plotting to carry out suicide bombings in the country.

Authorities say JI has some links to Al-Qaeda, and was responsible for attacks including the October 2002 bombings in Bali, Indonesia that left 202 mostly foreign tourists dead.

"We don’t want a repeat of what happened in Makati several months ago," Ermita said, referring to simultaneous Valentine’s Day bomb attacks by the Abu Sayyaf in Manila’s financial district, Davao and General Santos cities. Six people died and dozens were wounded.

Police said they have arrested three suspected Abu Sayyaf rebels in connection with Wednesday’s attack in Zamboanga.