To Indonesia's north, not far from the southern Philippines, sits a cluster of Indonesia's outermost islands.

Key points: Terrorism analyst says handguns found last week were destined for use by terrorists in Indonesia

Terrorism analyst says handguns found last week were destined for use by terrorists in Indonesia Indonesia's Tinakareng island could be used for illegal transit and storage of weapons

Indonesia's Tinakareng island could be used for illegal transit and storage of weapons George Brandis says that Indonesia and Australia need to tackle the issue

A gateway between two nations, about 200 kilometres from the North Sulawesi capital Manado.

Last week, on one of those islands the military uncovered buried weapons. The handguns were later confirmed to be from the Philippines.

According to Indonesian terrorism analyst Adhe Bhakti they were almost certainly destined for use by terrorists in Indonesia.

There is now concern that Tinakareng island, where the weapons were found, could be used not only for the illegal transit of weapons but also be a place of storage.

"With the recent findings it may show that Tinakerang is used as a storage island until they find the right time to smuggle the weapons," Mr Bhakti said.

"I can assure you that the weapons will be used for an attack in Indonesia, the question is where, when and by which group? That's what we don't know yet."

Two handguns, illegally trafficked into Indonesia from the Philippines, were used by the perpetrators of the terrorist attack in central Jakarta in January last year.

Indonesian military uncovered buried handguns that were later confirmed to be from the Philippines. ( ABC News )

Indonesia, the Philippines and Malaysia have begun trilateral patrols in the nearby Sulu and Celebes seas but the borders are many and easy to slip through.

"The coastlines are so long, how will they be able to cover all that?" Mr Bhakti questioned.

And he had a warning.

"It's like the tip of the iceberg, there could be many more weapons than police have found."

In Manado, ministers from Australia, Indonesia, the Philippines, Malaysia, New Zealand, and Brunei are gathering to discuss a regional approach to combating terrorism and reducing the risk posed by foreign fighters returning from the Middle East and the Philippines.

Attorney-General George Brandis, who is co-chairing the meeting, said after arriving in the North Sulweisi capital that Indonesia and Australia needed to tackle the issue.

"We realise that this is a problem that needs to be attacked both bilaterally, and Indonesia and Australia work closely together and have done so for a long time, and also multilaterally in forums such as this," he said.

Dozens of Indonesians allegedly join fighting in Marawi

With fighting in Marawi now entering a third relentless month the gathering could not come at a more pressing time for the region.

The challenge will be for the nations not known for the bilateral cooperation or intelligence-sharing in the past to let down historical barriers so true cooperation can emerge.

"While governments around the region and particularly the 'frontline' states of Indonesia, Malaysia and the Philippines recognise the need for greater regional cooperation, there remain formidable obstacles to working together," a recent report from the Institute of Policy Analysis of Conflict noted.

"These include deep-seated political distrust between the Philippines and Malaysia that impedes information sharing."

Terrorism expert says there could be many more weapons than what the police have found. ( ABC News )

There are thought to be between 20 and 40 Indonesians who have joined the fighting in Marawi. They pose a serious threat if they manage to return home.

"They have the capability for violence, as they have been trained to use weapons and explosives for a terrorist attack," Mr Bhakti said.

"With the number of Indonesians in the Philippines and the number of Indonesians who have returned from Syria, I'm sure they have the skill already and they could have the intention or the will to conduct the same violence in Indonesia."

But he stressed there remains a lack of coordination within and between Islamic State group affiliated terrorist groups in Indonesia, limiting their ability to launch a large-scale attack.

"Inspired yes, they are inspired but they don't have the capacity yet," Mr Bhakti said.