The several district courts of the United States are vested with jurisdiction specifically to enforce the provisions of this subchapter. If and when the Secretary shall so request, it shall be the duty of the several United States attorneys in their respective districts, under the direction of the Attorney General, to institute proceedings to collect the penalties provided in this subchapter. The remedies and penalties provided for herein shall be in addition to, and not exclusive of, any of the remedies or penalties under existing law. This section also shall be applicable to liquidated damages provided for pursuant to section 1349 of this title.