The Indonesian authorities have tightened security in Bali after reports at the weekend of a suspected militant plot to attack the holiday island.

“In connection with information about a terror arrest and a planned action in Bali, we are increasing security at all points of entry into Bali,” said provincial police chief Sugeng Priyanto.

“The focus of our attention is also the small ports that are spread out around Bali.”

Informal points of entry are being monitored as well, he added.

Anti-terror police said they were investigating whether a suspected militant who was arrested last week, whom some press reports refer to only as “DA”, was plotting an attack in Bali. Police found a bomb and “high-impact explosive materials” during a raid at the suspect’s house.

“The suspect told us in a statement that they were planning an attack in Bali but there are no details or timeline,” said national police spokesman Agus Rianto.

In 2002, Bali became the site of Indonesia’s deadliest terror attack. A nightclub bombing on the resort island carried out by home-grown militants killed 202 people, mostly Australians, and prompted a nationwide security crackdown.

According to Mr Rianto, DA is a suspected member of the terrorist network run by Indonesian militant Bahrun Naim, who was linked to the Islamic State in Iraq and Syria (ISIS), reported the Daily Mail Online.

DA was caught on Monday last week in Lampung, Sumatra, for his alleged role in a July 5 suicide bomb attack on a police station in Surakarta, also known as Solo, in Central Java.

About five million rupiah (S$510) is said to have been transferred to people in Bahrun Naim’s network in Indonesia to carry out the Surakarta blast and the planned attack in Bali, Mr Rianto said on Friday.

The arrest was among a series of terrorism-related arrests across several cities in Indonesia last week as the authorities intensified a security crackdown in the world’s largest Muslim-majority country.

Indonesia has seen a recent resurgence in radicalism, inspired in part by ISIS. The country saw its first ISIS-linked attack in January this year when four militants carried out a gun and bomb attack in a busy commercial district in the capital Jakarta.

“My impression is that, honestly, ISIS militants are not too strong here,” Mr Taufik Andrie, executive director of Jakarta’s Institute for International Peace Building, told The Australian.

He said: “Even though there are a lot of fatwas and guidance and instructions from Indonesian fighters in Syria, their ability to carry out an attack here is very limited right now.”