Five members of an extended family who had been living in squalid conditions on a remote New Mexico compound where the body of a three-year-old boy were found, been charged over a conspiracy to carry out jihadist attacks on US targets.

Siraj Ibn Wahhaj, 40, his girlfriend Jany Leveille, 36, a Haitian woman allegedly in the US illegally, her two sisters, Hujrah Wahhaj and Subhanah Wahhaj, and her brother-in-law, Lucas Morton, were indicted on Wednesday by a grand jury.

The charges listed in the indictment relate to terrorism, kidnapping, and conspiracy to provide resources, training and other support for 'attacks to kill officers and employees of the United States,' the Department of Justice said.

According to the indictment, the five defendants had, from October 2017, 'maintained a training compound to prepare for attacks on government, military and other institutions.'

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Siraj Ibn Wahhaj, 40, (left) and his girlfriend Jany Leveille, 36, (right) were indicted on Wednesday by a grand jury

Wahhaj and the others have been arrested in August following a raid on their New Mexico desert compound (pictured from the air)

The remains of Wahhaj's three-year-old son (pictured) were found at the high-desert site

Siraj and his girlfriend 'instructed persons, including other occupants of the training compound, to be prepared to engage in jihad, to die as martyrs and to engage in violent acts,' including the killing of FBI employees and military personnel, the document alleges.

The suspects have been in federal custody since August on firearms charges, after authorities first descended on their ragged camp near Amalia, just south of the Colorado state line.

A search for a missing Georgia boy - the son of suspect Siraj Ibn Wahhaj - had led law enforcement to the site on the high-desert where they found the child's remains as well as 11 starving children dressed in rags and living in filth.

Authorities also have accused Wahhaj and others of transporting weapons across state lines to New Mexico, and training children at a firing range on the property to carry out school shootings and other attacks that never occurred.

Sisters Subhanah Wahhaj, 35, (left) and Hujrah Wahhaj, 38, (right) are also among the five suspects indicted on charges related to terrorism, kidnapping, and conspiracy

Lucas Morton, Leveille's brother-in-law, is also accused of plotting to attack police officers, military personnel and government officials

Police discovered 11 starving children living in filth in the ragged camp with no food or water

The suspects' attorneys have disputed the allegations, saying they are based on the uncorroborated statements of children.

'The defendants in this case allegedly were preparing for deadly attacks and their targets included law enforcement and military personnel, the very people who are committed to protecting all of us,' Michael McGarrity, director of the FBI's Counterterrorism Division, said in a statement Thursday.

All the suspects, except Wahhaj, also have been charged with participating in the kidnapping of Abdul-ghani Wahhaj, the special-needs boy who died after prosecutors say he had been denied medication for seizures.

Jany Leveille, a leader of the group, believed medication suppressed Muslim beliefs, authorities said.

Because authorities say the 2017 abduction ultimately resulted in the boy's death, the kidnapping count against Leveille, Hujrah Wahhaj, Subhana Wahhaj and Lucas Morton carries a potential sentence of life in prison or the death penalty should prosecutors win a conviction against them and decide to pursue the maximum punishment in the case.

The father has not been charged with kidnapping because of federal statutes that generally only allow for charging parents with abducting their own children in international cases.

The results of an autopsy for the boy whose remains were found at the compound property are still pending.

Defense attorneys said they were awaiting more information on the new charges before providing further comment.

'We still don't have all the documents from the government regarding this case,' said Amy Sirignano, who represents Morton.

She said in an email sent on behalf of the defense that their clients would plead not guilty at an arraignment scheduled for next Thursday.

A lawyer for the suspects, among them Leveille and Wahhaj (pictured in court in August) said they plan to plead not guilty to the new federal charges

The suspects remain jailed after a federal judge ruled in September that they could not be freed on bail as they await trial.

Federal authorities said Siraj Ibn Wahhaj and Leveille, who lived as a couple at the compound, had performed daily, hours-long prayer rituals over Wahhaj's young son in the days leading to his death - even as he cried and foamed at the mouth.

Leveille, who believed in 'black magic,' allegedly wanted to 'exorcise' the toddler, who suffered a brain injury at birth.

An FBI agent also said in federal court that Leveille's two teenage sons had described how she expected the dead child to be resurrected as Jesus and provide instruction to get rid of corrupt institutions that involve teachers, law enforcement and banks.

A prior federal grand jury indictment on firearms and conspiracy charges against the group stemmed from accusations that Leveille, who is originally from Haiti, had been living in the country illegally and that the others had conspired to provide her with firearms and ammunition.