Hillary Clinton's campaign team released a new attack ad Monday questioning Donald Trump's alleged ties to Russian President Vladimir Putin.

The GOP nominee has stated his admiration for the Russian president repeatedly, calling him a "strong leader" and a "man so highly respected within his own country and beyond," and new reports suggest Trump's campaign manager, Paul Manafort, has some questionable ties to Russian oligarchs.

"We don't know why Trump praises Putin," the Clinton video said Monday. "We don't know why they share foreign policies."

"We don't know why Trump's top advisors have ties to Putin," it added. "We don't know why Russia is trying to influence this election or why he is inviting them to."

The latter comment from the ad is a reference to when Trump suggested last month that the Russians should help the U.S. find Hillary Clinton's unauthorized private State Department emails.

"We don't know how much Trump has invested in Russia or how much they've invested in him," the ad said.

"We don't know what's going on here, and Donald won't tell us," it concluded. "We'll let you guess."