The Indonesian Navy seized four small boats from the Philippines for illegal fishing and plans to sink them, pending court rulings.
"We will sink the boats just like we did to other boats," Indonesian Navy spokesman Commodore Manahan Simorangkir said on Thursday.
He said the court was still investigating the documents of the four boats.
Manahan said the boats were caught by Navy warship KRI Slamet Riyadi on Sunday 293 miles off East Tarakan, North Kalimantan.
The four boats, Van Boat (VB) Vien 09, VB Saint Thomas, VB Saint Jose and VB Santa Cruz, failed to show the proper permits.
"The boats are small, between 16 to 20 GT [gross tons], but they should have a fishing permit because each weighs more than 7 GT," Manahan said, adding that the Navy patrol arrested eight crew members and seized salted fish and squid from the boats.
Currently the boats, along with the crew, are at the Tarakan Naval Base in North Kalimantan.
Manahan said the crew would be sent to the immigration office immediately after they finished investigating the vessels.
A crew member, Yoyong, said he and his friends had been in Indonesian waters for seven days before being arrested.
"Here we get plenty of fish of good quality. In the Philippines it is not as good and plenty as it is here," he said in broken Indonesian, as quoted by a newspaper in East Tarakan.
He said he did not understand that there was a marine border between Indonesia and the Philippines.
Indonesia has arrested and sunk many illegal fishing boats from the Philippines, mostly small fishing boats.
Both countries are archipelagic and many fishermen do not recognise their country's border during fishing activities.
In December, for instance, the Indonesian authority arrested four illegal fishing boats from the Philippines and the boats were sunk after the crew failed to show the proper documents for their fishing activities in Indonesia.
Two more vessels from the Philippines were caught in the Celebes Sea on Jan. 24 by the Maritime Affairs and Fisheries Ministry.
The case for these boats and their crew is still being processed at court.
The Indonesian Navy is under fire as it only catches illegal small fishing boats and allows the bigger vessels explore the country's waters.
On Wednesday, for instance, Maritime Affairs and Fisheries Minister Susi Pudjiastuti urged the Indonesian Navy to arrest a Chinese vessel Fu Yuan Yu-80, which is still spotted in Indonesian maritime territory despite its expired shipping permit.
However, the Indonesian Military (TNI) claimed the vast maritime territory and lack of equipment were its biggest obstacles in catching larger boats.
Indonesia loses about Rp 300 trillion (S$32 billion) annually due to illegal fishing. Currently, there are some 5,400 illegal ships operating in Indonesia's territory.
President Joko "Jokowi" Widodo has instructed law enforcers to take firm action against foreign ships stealing fish from Indonesian waters, including by sinking them on the spot.