It’s been revealed two “repeat offenders” from Indonesia have been jailed after being caught fishing illegally in far-north Western Australia earlier this month.

It comes as the Australian Border Force (ABF) reports a “massive surge” in illegal fishing across northern Australia in recent weeks, with two more vessels intercepted in the Kimberley Marine Park.

The jailed men were among 20 illegal fishers sentenced in a Darwin court  last week, after authorities intercepted four vessels in Kuri Bay, about 370 kilometres north-west of Broome on August 6.

An Australian Fisheries Management Authority (AFMA) spokesperson confirmed on Wednesday afternoon that several of those fishers “were identified as having a previous history of fishing illegally in Australian waters”.

Of that group, two men were found by Northern Territory Police, the Australian Federal Police and the Commonwealth Director of Public Prosecutions to have had outstanding warrants issued against them for similar offending.

AFMA said the warrants were executed after the pair’s court appearance on Friday afternoon, with the men fined $4,000 and sentenced to 15 days and 75 days in jail respectively.

The other 18 illegal fishermen were fined and handed recognisance orders, similar to good behaviour bonds.

The group will be returned to Indonesia by the ABF.

ABF Assistant Commissioner Chris Waters told ABC Perth Radio on Tuesday that since August 18, authorities had detected seven more illegal fishing vessels in waters off northern Australia, from the Timor Sea to the Kimberley.

In total authorities seized over 4,500 kilograms of fish, more than 1,100kg of sea cucumber and 2,000kg of salt used to preserve the catch from the vessels.

AMFA fisheries operations general manager Justin Bathurst told ABC Radio National on Wednesday that financial gain was a driving factor behind the surge.

“I suppose the risk of being caught is potentially lower than potential gain financially … as a result of illegal fishing,” Mr Bathurst said.

Federal Shadow Home Affairs Minister James Paterson said the number of foreign fishing vessels was a national security and biosecurity risk.

Senator Paterson said there also needed to be more transparency on operational matters, “unless there are very good operational reasons”.

“I think the Australian people have a right to know what’s happening, what is failing and why it’s not working,” he said.

Mr Waters said authorities were well-resourced to monitor the coastline.

“The area of operation we’re talking about is twice the size of Victoria,” he said.

Authorities said they would continue hold public information campaigns in Indonesia to inform communities about the risks of illegal fishing.