The district courts of the United States and the district courts of the Territories, from time to time, shall increase the number of United States magistrate judges, so as to afford a speedy and convenient means for the arrest and examination of persons charged with the crimes referred to in section 1987 of this title; and such magistrate judges are authorized and required to exercise all the powers and duties conferred on them herein with regard to such offenses in like manner as they are authorized by law to exercise with regard to other offenses against the laws of the United States. Said magistrate judges are empowered, within their respective counties, to appoint, in writing, under their hands, one or more suitable persons, from time to time, who shall execute all such warrants or other process as the magistrate judges may issue in the lawful performance of their duties, and the persons so appointed shall have authority to summon and call to their aid the bystanders or posse comitatus of the proper county, or such portion of the land or naval forces of the United States, or of the militia, as may be necessary to the performance of the duty with which they are charged; and such warrants shall run and be executed anywhere in the State or Territory within which they are issued.