This article is more than 1 year old

This article is more than 1 year old

The threat of Islamic State is mounting again in the Philippines, with estimates there could be between 40 to 100 foreign fighters, and a growing momentum among local pro-Islamic State militant groups.

In May last year, the Mindanao city of Marawi was overrun by Isis fighters and a caliphate declared. It took a bloody, five-month siege by the army, in which 1,200 lives were lost, for the government to regain control.

But one year on from Marawi’s liberation, Prof Rommel Banlaoi, chairman of the Philippine Institute for Peace, Violence and Terrorism Research, told the Guardian that he had seen records of up to 100 foreign fighters on the island – a combination of old and new arrivals since the Marawi siege last year – who want to re-establish the east Asia wilayah (or East Asia Isis province) crushed in the fighting.

Banlaoi said the fighters in Mindanao had mainly travelled from neighbouring Indonesia and Malaysia but also Pakistan, Bangladesh and the Middle East.

Marawi one year after the battle: a ghost town still haunted by threat of Isis Read more

A high-ranking intelligence officer gave figures of that closely matched Banlaoi’s records. “There are about 40 foreign fighters remaining in the country, but 40 others are in the watchlist,” said the officer, who asked to remain unnamed because because he was not authorised to speak to the media.

The presence of foreign fighters is known to energise and embolden local pro-Isis groups and there are increasing concerns of a renewed bid to declare a caliphate in Mindanao.

Facebook Twitter Pinterest A resident of Marawi returns to her home in April - the first time since she fled the fighting in the city. Photograph: Ted Aljibe/AFP/Getty Images

The threat is highlighted by an apparent suicide bombing by a foreign fighter from Morocco in July that killed 11 people. It was claimed by Isis as a “martyrdom” operation.

There is also continuing support for Isis-affiliated groups among local Muslims, many who are still displaced from the Marawi conflict or disaffected by widespread corruption and broken government promises of peace and autonomy in Mindanao. “The risk of violence continues to be very high, more from local pro-Isis elements,” said Sidney Jones, director of the Institute for Policy Analysis of Conflict.

For decades Mindanao has been a centre for Islamist militant groups but after the Isis caliphate was declared in 2014 in Syria and Iraq, several of the groups formed a pro-Isis coalition. They included factions of Bangsamoro Islamic Freedom Fighters (BIFF), Abu Sayyaf, Ansar al-Khilafah and Maute.

In May 2017, hundreds of militants descended violently on Marawi and flew the Isis flag over the city.

Around 80 foreign fighters were amongst them and the conflict prompted an upsurge in Isis propaganda focusing on southeast Asia. One video, titled Inside the Caliphate, urged Isis supporters to travel to the Philippines.

Facebook Twitter Pinterest Displaced Marawi city residents living in temporary shelters in May. Tens of thousands were displaced and about half the city’s infrastructure was destroyed in the fighting. Photograph: Jes Aznar/Getty Images

​Foreign fighters play a very important role in bridging the parochial divides between Filipino groups Zachary Abuza

With the fall of the Middle Eastern caliphate in October 2017, this year has seen an unprecedented number of Europeans, including those from the UK, Spain, Germany and Switzerland, attempting to travel to the Philippines to join Isis ranks there.

“Foreign fighters are in the Philippines because they consider the country, particularly Mindanao, as a safe haven, alternative home base and a new land of jihad,” explained Banlaoi, who said he had seen a lot of chatter on the east Asia wilayah on Isis social media recently.

“They train and learn from local fighters. They provide funds. They provide a global support network.”

The military, keen to show they have control over the situation, disputed Banlaoi’s numbers. The secretary of defence, Delfin Lorenzana, told the Guardian: “I don’t think there are more than 10.”

Lt Gen Arnel Dela Vega, Western Mindanao Command Chief, said they had been working with Malaysia and Indonesia to stop more foreign fighters crossing the border, emphasising “we’ve blocked the backdoor”.

In Malaysia, Ahmad el-Muhammady, who consults with the authorities on de-radicalisation of Islamist militants, said the concern over foreign fighters in Mindanao was growing and “the Malaysian intelligence community is closely monitoring the situation”.

Facebook Twitter Pinterest Soldiers patrolling Marawi during heavy fighting in June 2017.

Photograph: Jes Aznar/Getty Images

As well as often having more experience with conflict, foreign fighters “play a very important role in bridging the parochial divides between Filipino groups” said Zachary Abuza, south-east Asia analyst at the National War College.

“Look at Marawi [and] what happens with Philippine-based Isis groups work together. And often foreign fighters try to cajole local militants to escalate the violence.”

Abuza calculated there were up to 40 foreign fighters in Mindanao and he emphasised the serious threat they posed, especially when combined with a flourishing local allegiance to pro-Isis groups in Mindanao.

“Many seek the relative sanctuary of the southern Philippines,” he said. “There they can regroup, train and plot attacks. With Isis’s declaration of an east Asia wilayah, the southern Philippines becomes more important because there is enough ungoverned or very poorly governed space.”

“There are Isis cells in Malaysia and Singapore but they don’t control any territory,” added Abuza. “You can’t be province of the caliphate without territory.”