Image copyright Getty Images Image caption File photo: ICE agents detain a suspected gang member in Los Angeles, 2015

The United States Immigrations and Customs Enforcement (ICE) has arrested 1,378 people over the last six weeks in a massive gang-related operation.

Of those, 1,095 were confirmed as gang members, ICE said, while the remaining 238 "were arrested on either criminal or administrative charges".

More than 900 of the arrested were US citizens.

Acting director Thomas Homan said "violent criminal street gangs are the biggest threat facing our communities".

Media playback is unsupported on your device Media caption Nisa Mickens, 15, was killed by an MS-13 gang including undocumented immigrants.

The Homeland Security Investigations (HSI) unit carried out the operation, its largest to date.

ICE said it was targeting gang members and "associates" involved in cross-border criminal activity - including drug and weapons smuggling, sex trafficking and murder.

During the six-week operation, 238 firearms were seized, alongside almost 600lb (270kg) in mixed drugs, and almost half a million dollars in cash.

Those arrested were considered "confirmed" as gang members, ICE said, if they admitted to membership, had been convicted of gang-related offences, had tattoos of a specific gang, or were identified "by a reliable source".

Image copyright Getty Images Image caption Inspecting gang tattoos is common practice (file photo)

Of the 1,378 people arrested:

137 were affiliated with the Bloods gang of Los Angeles

104 were part of the Crips, also of Los Angeles

118 with the Surenos, a Mexican-American affiliation

104 with MS-13, born in LA but with roots in El Salvador

283 had no gang affiliation.

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ICE also said that 10 people arrested had entered the US as unaccompanied minors - and nine of them were gang members. Another three had been part of the Deferred Action for Childhood Arrivals (DACA) scheme - so called "dreamers", or undocumented immigrants who arrived as children who are allowed to stay,

"Aliens granted DACA who are found to pose a threat to national security or public safety may have their deferred action terminated at any time and the Department of Homeland Security may seek their removal from the United States," ICE said in its press release- adding that about 1,500 people have been deported for that reason since 2012.

The large-scale operation was part of Operation Community Shield, an ongoing programme which targets gang members with the help of federal and local law enforcement agencies.