U.S. Democratic presidential candidate Bernie Sanders accused front-runner Hillary Clinton of apparent campaign finance violations on Monday, ratcheting up the rhetoric against his rival one day before New York state's crucial primary elections.

Sanders questioned whether Clinton's campaign violated legal limits on donations by paying her staff with funds from a joint fundraising effort by Clinton and the Democratic National Committee, or DNC.

Sanders has long maintained that the DNC has favored Clinton over him. The U.S. senator from Vermont is a democratic socialist who has run as an independent in his Senate campaigns.