Hillary Clinton's campaign has blamed Russia for an embarrassing leak of emails from the Democratic National Committee, propelling the Kremlin to the heart of American political debate as tensions between Moscow and Washington linger months before the historic vote.
Trump denied allegations of ties with Moscow today, telling voters in Florida that he had "nothing to do with Russia."
"I said (Russian leader Vladimir) Putin has much better leadership qualities than (US President Barack) Obama, but who doesn't know that?" he said.
"President Putin has repeatedly said that Russia has never interfered and does not interfere in internal affairs, especially in the electoral processes of other countries," Kremlin spokesman Dmitry Peskov told reporters.
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Peskov had earlier dismissed as "absurd" claims that Russia was involved in the hacking of emails that were released by WikiLeaks.
"Moscow has carefully avoided any actions, any words that could be interpreted as direct or indirect influence on the electoral process," Peskov said.
"If you talk about some suspicions regarding our country, then you need at the very least to be precise and concrete," he added.
Obama told NBC he could not speak about the precise motive for the hack or subsequent leak but was aware of Trump's comments about the Russian leader.
"What we do know is that the Russians hack our systems. Not just government systems, but private systems," Obama said.
Russian political analysts say that the Kremlin has always preferred working with Republican politicians.
"The Kremlin has traditionally considered that a Republican administration is more convenient because it is more pragmatic," independent analyst Nikolai Petrov told AFP.
In December last year, Putin praised Trump as "a very striking man, unquestionably talented".
Trump today said he had never met Putin but cast doubt over accusations that Moscow was behind the hack.