In an interview on Sunday on ABC's "This Week," Mook told host George Stephanopoulos that the Republican presidential nominee and his campaign's ties to Russian President Vladimir Putin's regime suggested the real-estate mogul could be appeasing Russian state interests, Business Insider wrote.

"We need Donald Trump to explain to us the extent to which the hand of the Kremlin is at the core of his campaign," Mook said.

"There are real questions being raised about whether Donald Trump himself is just a puppet for the Kremlin in this race."

Read alsoUkraine's anti-graft agency reveals details of secret ledgers with Trump's campaign chiefMook asserted that Trump's actions indicated a cozy relationship with Russia, noting Trump's favorable comments about Putin and the campaign's successful push to soften language in the Republican Party platform that would've mandated providing weapons to Ukraine.

Clinton's campaign manager also noted several Trump advisers' ties to Russian organizations, including former Defense Intelligence Agency Director Michael Flynn's relationship with Russia Today, a state-sponsored Russian news network.

"There are a lot of questions here and we need Donald Trump to disclose all of his financial ties and whether his advisors are having meetings with the Kremlin," Mook said.

Over the past several days, the Trump campaign has worked to play down potential links between the real-estate magnate and Russia.

Last week, former Trump Campaign Chair Paul Manafort resigned amid growing revelations about his deep financial ties to former Ukrainian President Viktor Yanukovych, who was backed by Putin.