Washington - US President Donald Trump lashed out Thursday at Democrats for investigating his dealings with Russia, saying his opponents are "going nuts."
"PRESIDENTIAL HARASSMENT! It should never be allowed to happen again!" Trump tweeted.
He said that an expansion of the probe by the intelligence committee in the Democrat-led House of Representatives was unprecedented.
Adam Schiff, the congressman heading the committee, said it will look into suspicions of collusion between Trump and Russia and also broader allegations of financial wrongdoing in Trump's inner circle.
The powerful committee will be working in parallel with an already well-advanced probe by special prosecutor Robert Mueller into alleged links between Trump and Russian agents during his 2016 election campaign.
"Congressman Adam Schiff announces, after having found zero Russian Collusion, that he is going to be looking at every aspect of my life, both financial and personal, even though there is no reason to be doing so. Never happened before!" Trump tweeted.
Trump has repeatedly declared his innocence, claiming that the growing investigations, which also include probes by federal prosecutors in New York, are politically motivated.
However, Mueller alone has already brought charges leading to indictments of six people with ties to Trump in the Russia collusion probe.
And critics say the secrecy around the financial workings of Trump's real estate empire and his years of interest in doing business in President Vladimir Putin's Russia make a troubling backdrop that requires deeper probing.