Six suspected Islamic militants killed in a standoff with police were planning to attack police officers in Indonesia’s East Java province to seek revenge for the arrest of a radical leader, authorities said Sunday.

The men were cornered in a village in Tuban district Saturday after attempting to shoot a traffic police officer who was approaching them when he saw their car stopped along the roadside, said national police spokesman Rikwanto.

Indonesia: Militants Killed in Standoff Planned to Attack Police

The six refused appeals to surrender during a standoff that lasted several hours and were fatally shot by police, said Rikwanto, who goes by a single name.

Indonesia: Militants Killed in Standoff Planned to Attack Police

On Friday, counterterrorism police arrested three suspected militants who were allegedly planning to attack a police station in East Java. Among those arrested was Zainal Anshori, a senior figure of Jemaah Anshorut Daulah, an umbrella group of Indonesian extremists that claims allegiance to the Islamic State group.

Indonesia: Militants Killed in Standoff Planned to Attack Police

Rikwanto said that Anshori had orchestrated Saturday’s planned attack.

“They had acted on Anshori’s order as a revenge of his arrest,” said Rikwanto, citing police interrogation of other arrested militants.

Police said they seized dozens of rounds of ammunition, several firearms, knives, jihadi books and a car used by the men.

Muslim-majority Indonesia has been cracking down on militants since the 2002 Bali bombings by al-Qaida-affiliated radicals that killed 202 people, mostly foreigners. A new threat has emerged in the past several years from Islamic State group sympathizers.