Two men have been arrested and charged with plotting to attack a military processing center in Seattle with grenades and machine guns.

Abu Khalid Abdul-Latif of Seattle and Walli Mujahidh of Los Angeles were arrested on Wednesday evening in a seven-count complaint accusing them of conspiracy to murder officers and employees of the United States, conspiracy to use grenades and other firearms offenses, says a Reuters report.

Authorities were alerted earlier to the plot this month by someone who had been approached to participate by Abdul-Latif and supply weapons, the report said, citing the Justice Department. The unidentified person then agreed to work with authorities as they monitored the plot.

The two men had originally planned to attack the Joint Base Lewis-McChord in Washington state but then switched targets to the place where military enlistees are screened and processed, said the report.

Abdul-Latif told the cooperating individual the attack would be to retaliate for alleged crimes by U.S. soldiers in Afghanistan, according to the report.

"Abdul-Latif explained that, in his view, murdering American soldiers was justifiable," the affidavit said. The two were provided weapons that were brought by the cooperating individual but had been rendered inoperable by authorities.