KUALA LUMPUR: Malaysia's premier has called a deadly incursion by Philippine militants a "wake-up call" that will lead to tighter security on the neighbours' notoriously porous sea border, a report said Wednesday.

But Prime Minister Najib Razak added that securing the border was a "huge challenge" due to eastern Sabah state's long coastline and the centuries-old movement of people between there and the adjacent southern Philippines.

"This is a wake-up call. There are gaps in terms of our capabilities, but we hope we will be able to close the gaps," Najib said in an interview published in the New Straits Times newspaper.

"For example, the coastline of Sabah is simply enormous," he was quoted as saying.

The issue burst into the regional spotlight last month when armed followers of a self-styled Philippine sultan landed in Sabah to claim the territory for their leader, tearing open a long-dormant dispute over ownership of the state at the northern tip of Borneo island.

The incursion by some 200 Islamist militants and an ongoing counter-offensive by Malaysian security forces has left dozens dead -- mostly the invaders -- and put rare a stress on relations with Manila.

Security forces are still hunting for militants, possibly scores of them, who managed to dodge a military operation to round them up.

Najib's administration has been criticised by the opposition for the porous nature of the border and must balance calls for tighter security with the task of managing cross-border movement.

Najib gave no details of how the border would be better policed, but said "we certainly need to put in more assets".

"We will certainly put in place a better surveillance system and tighten up security in Sabah," he added.

Today's national borders are a relatively new phenomenon for sea-faring people in the area accustomed to sailing freely between Sabah and the lightly-governed southern Philippines.

Many families on both sides have relatives across the border.

Domestic critics widely accuse Malaysia's government of capitalising on the open borders by providing residency to possibly hundreds of thousands of Muslim Filipinos and Indonesians in recent decades.

The charge has been supported by the testimony of former officials before an ongoing inquiry.

Critics say the scheme sought to increase the Muslim population of Sabah, to boost support for Malaysia's Muslim-dominated ruling coalition.