Thousands of soldiers in El Salvador have surrounded a rural region larger than New York City to flush out gang members who are allegedly hiding there.
The military deployment in Cabañas was ordered by President Nayib Bukele as part of his ongoing war on gangs.
More than 70,000 suspected gang members have been arrested since a state of emergency was declared in March 2022.
Thousands of people with no discernible link to gang activity have also been swept up in the dragnet of arrests.
Lorries loaded with soldiers were seen on the streets of the regional towns of Tejutepeque and Ilobaso on Tuesday, AFP news agency reports.
"Since this morning, 7,000 soldiers and 1,000 police officers have established a security fence," Mr Bukele posted on X, formerly known as Twitter.
The president said that his government's security strategies had succeeded in dismantling the gangs in the country's large urban centres and forced them into hiding in rural areas.
This latest operation was aimed at "completely surrounding them" and "extracting them from their hideaways", he added.
The president stressed that the siege would not be lifted until "all the criminals" were apprehended. At the same time, he assured Salvadoreans that "honest people, visitors and tourists have nothing to fear" but did not clarify how the security forces would distinguish between the two groups.
Cabañas is an agricultural region which covers an area of just over 1,000 sq km (390 sq miles) and is home to more than 160,000 people.
It is not clear whether residents will be able to leave the area while the military siege is under way and how they would be able to "go about their normal activities" as the president said they would.
It is not the first time the security forces have sealed off a whole area. In December, troops surrounded the city of Soyapango as part of a gang crackdown.
Rights groups have been highly critical of the mass arrests carried out under the state of emergency, saying they have led to thousands of people being arbitrarily detained.
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There are also concerns about a recent move by the country's lawmakers to allow mass trials.