Trump not exculpated for acts that he allegedly committed: Mueller

US President Donald Trump was not exculpated for the acts that he allegedly committed, former special counsel Robert S Mueller told American lawmakers on Wednesday.

Mueller is testifying publicly before two separate congressional panels on Wednesday and for the first time addressing questions about his investigation of President Trump and Russian interference in the 2016 presidential election.

"The finding indicates that the President was not exculpated for the acts that he allegedly committed," Mueller, who recently submitted the results of his over two years of investigations on the alleged Russian interference in the 2016 presidential elections, said in response to a question.

He again declined to accuse the US president of a crime.

In high-stakes testimony, Mueller also said that the Russians engaged in sweeping interference in the 2016 election.

President Trump appeared to be watching the much sought after Congressional hearing.

"Mueller was asked whether or not the investigation was impeded in any way, and he said no." In other words, there was NO OBSTRUCTION," Trump tweeted.

"I would like to thank the Democrats for holding this morning's hearing. Now, after 3 hours, Robert Mueller has to subject himself to #ShiftySchiff - an Embarrassment to our Country!" Trump tweeted.

During the course of his investigation, the 74-year-old former FBI chief and veteran prosecutor charged more than 30 defendants with committing federal crimes, including 12 officers of the Russian military.

Seven defendants have been convicted, Mueller said.

In his first Congressional testimony after he submitted his report, Mueller said that his investigation found that the Russian government interfered in US elections in sweeping and systematic fashion.

"The investigation did not establish that members of the Trump campaign conspired with the Russian government in its election interference activities," he told members of the House Judiciary Committee.

"We did not address collusion, which is not a legal term. Rather, we focused on whether the evidence was sufficient to charge any member of the campaign with taking part in a criminal conspiracy, and it was not," he added.

"Our investigation of efforts to obstruct the investigation and lied to investigators was of critical importance. Obstruction of justice strikes at the core of the government's effort to find the truth and to hold wrongdoers accountable," he said.

Mueller said that he also investigated a series of actions by the president towards the investigation.

"Based on Justice Department policy and principles of fairness, we decided we would not make a determination as to whether the president committed a crime. That was our decision then and remains our decision today," he said.

In response to a question, Mueller agreed that his report did not conclude that Trump did not commit obstruction of justice. He asserted that it would be unconstitutional to indict a sitting president.

Commenting on the development, White House Press Secretary Stephanie Grisham said the last three hours have been an epic embarrassment for the Democrats.

"Expect more of the same in the second half," Grisham said.