Suffolk County is now in “a state of war,” says Police Commissioner Timothy Sini — at war with Mara Salvatrucha, the Central American transnational crime cartel better known as MS-13, and its growing spree of murder.

Sini made his declaration after the corpses of four young men turned up in a Central Islip park — with a video of the bodies sent to the girlfriend of one teen.

The slayings, said the commissioner, were “consistent with the modus operandi of MS-13.” The boys were beaten to death, then mutilated with hatchets.

This follows by weeks the arrest of several MS-13 members in the savage killings of three teens in nearby Brentwood. The skeletal remains of several other young victims have turned up, too.

Cops have made hundreds of arrests, but Sini warns the war won’t end anytime soon.

After all, MS-13 — notorious for its elaborate tattoos and its unremitting violence — has perhaps 70,000 members all told.

Street-level MS-13ers deal drugs and are expected to “put in work”: kill rivals or those who don’t pay the gang sufficient respect. The recent death toll in Suffolk alone is 11.

Those who refuse to kill are themselves targeted for death. One of the latest victims reportedly left computer messages saying, “I don’t want to do these things anymore.”

The gang’s core consists of immigrants (many illegal) from El Salvador. They’re precisely the kind of “bad hombres” President Trump has vowed to deport — and keep out.

The pages of The Post have been filled with stories of MS-13 killers who’ve been repeatedly deported, only to make their way back to New York. And Trump’s critics are no help: Mayor de Blasio’s nonsensical “sanctuary city” policy has even protected MS-13 members from the feds.

But even The Wall won’t keep MS-13 out: The gang has ample resources to enter America without crossing the Mexican border.

The FBI is helping in Suffolk, but the feds have been on the case as MS-13’s tentacles spread across the nation.

Stomping out gangs like MS-13 ought to be a priority for the entire Justice Department. At the least, Trump and Attorney General Jeff Sessions better have Suffolk County’s war in mind as they choose the next US attorney for the Eastern District.