Any action to enforce this chapter shall be forever barred unless commenced within 4 years after the cause of action accrued. For purposes of this section, a cause of action for a continuing violation is deemed to accrue at any time during the period of such violation. Whenever any civil or criminal proceeding is instituted by the federal government to prevent, restrain, or punish violations of the federal antitrust laws, the running of the period of limitations in respect of every right of action arising under this chapter, based in whole or in part on any matter complained of in the federal proceeding, shall be suspended during the pendency of said proceeding and for 1 year thereafter; provided, however, that whenever the running of the period of limitations in respect of a right of action arising under this chapter is suspended hereunder, any action to enforce such right of action shall be forever barred unless commenced within the period of suspension or within 4 years after the cause of action accrued.