Indonesia's presidential candidates pledged to get tough on terrorism as official campaigning began for the country's first direct leadership polls – a contest overshadowed by a deadly embassy attack.

In a televised discussion on the first of three days' official campaigning for the September 20 polls, incumbent Megawati Sukarnoputri defended her government's record on tackling militants, promising to step up security.

Speaking just days after her country was jolted by a fresh extremist attack, she tried to reassure voters that with her at the helm, Indonesia would remain a stable nation where a flourishing economy would alleviate widespread poverty.

Nine people were killed in an attack last Thursday on Australia's Jakarta embassy which police have blamed on the Al-Qaeda-linked Jemaah Islamiyah organisation held responsible for the 2002 Bali bombings and other strikes.

Megawati's uneasy television appearance, in which she answered questions from a selected panel, marked a departure for the president, who has made a policy of avoiding public events where she is required to stray from a script.

Her camp earlier this month refused a challenge to a televised debate from her former security minister Susilo Bambang Yudhoyono, who was clearly more at ease in front of the cameras during the discussion, offering jokes and asides as he laid out his policies.

The discussion is likely to be the most high profile event during the pre-poll campaigning which got off to a slow start on a day dominated by a series of bomb hoaxes at public buildings across the country.

Outlining her policies, Megawati defended her government's record on security, saying the latest attack could not easily have been prevented.

"Terrorism can take place anywhere. Let us take the example of the United States ... the Twin Towers September 11 incident could not be prevented and it took place.

"A bomb, even more so a suicide bombing done by using a vehicle or something that moves, even the experts said that there is nothing that can detect that," she said.

Amid warnings from Australian and Indonesian police that Islamic extremists blamed for the bombing were plotting further attacks, Megawati has put the country on "full alert" before the polls and ordered a huge security increase.

Yudhoyono, an ex general, also focused on tackling terrorism, saying the emphasis should be placed on giving intelligence agencies a preventative role.

"What is clear is that their ability for early detection must be enhanced. But what is also clear is that the intelligence [agency] does not work alone," he said adding that security forces must enhance cooperation.

Both candidates also covered the key issues of economic growth and alleviating poverty and broached the thorny subject of corruption, a major disincentive to vital foreign investment in Indonesia.

Megawati promised greater transparency while Yudhoyono said he would ensure anti-corruption bodies worked "effectively" to implement a five year plan aimed at vastly reducing graft.

Tuesday's debate is unlikely to dissuade voters already drawn to the former general by his suave personality and common touch. Megawati meanwhile will be left struggling to shed an aloof image that cost her support in a first round ballot in July.

In the latest opinion poll, taken before the embassy blast, Yudhoyono was out in front with Megawati closing the gap.

In the Indonesian Survey Institute study carried out in August, 61 percent preferred Yudhoyono over 30.3 percent for Megawati. A July survey by the same body showed 23 percent for Megawati and 68 percent for her rival.

The September 20 poll is the first time Indonesians will be able to directly elect their president and vice president, who were previously selected by legislators.