Former FBI Director Comey appeared before the US Senate Intelligence Committee on Thursday morning, with the US and international media and public closely following the hearing expected to last for several hours.

The hearing was divided into an initial open hearing followed by a closed session starting at 1 p.m. local time (1700 UTC) to cover questions related to security-sensitive issues.

Senate members hope to obtain answers on the greatest scandal of the Trump administration to date – Trump's shock firing of the FBI head and the alleged pressure from the president relating to the probe into Michael Flynn and his contacts with Russia. In a statement published ahead of time, Comey described Trump telling him he expected "loyalty" from him and asking him what can be done to "lift the cloud" of the Russia investigation.

"It's my judgment that I was fired because of the Russia investigation," Comey told the lawmakers at the public segment of the hearing.

"I was fired in some way to change, or the endeavor was to change, the way the Russia investigation was being conducted," he added.

Comey also said that there was "no doubt" in his mind that the Russian government tried to influence the 2016 election in the US through hacking, but added that he did not believe any of the votes were altered.

Comey concerned about lies

After taking an oath, Comey said that he decided to take notes after meeting Trump for the first time due to several factors, one of them being that he was "honestly concerned that [Trump] might lie about the nature of our meeting."

Acknowledging reports of their interviews being recorded, Comey commented "Lordy I hope there are tapes."

According to Comey, neither Trump nor any administration official asked him to halt the investigation into the alleged Russia collusion.

At the same time, Comey said it was "very disturbing" to hear Trump tell him "I hope you can let this go" on the probe into Flynn.

"I took it as a direction […] This is what he wants me to do," he told the lawmakers. "The context and the president's words was what led me to this conclusion."

Comey also said that he purposefully leaked his notes on Trump hoping that the media coverage would prompt the authorities to name a special prosecutor. US lawmaker subsequently appointed another ex-FBI head, Robert Mueller, as a special counsel to look into the alleged ties with Russia.

White House tried to 'defame' Comey

He also commented on the one-on-one dinner in January this year, when Trump allegedly asked him if he was interested in staying on as head of the FBI for the full term.

Comey said "common sense" told him that Trump was looking to get something in exchange for him keeping his FBI job.

Commenting on his firing, the ex-FBI head also said that the president repeatedly told him he was doing a "great job." He also claimed that Trump called him once for no other reason than to praise him and say he hoped he would stay on as FBI chief.

"So it confused me when I saw on television that the president actually fired me because of the Russian investigation," he said.

He also accused the administration of trying to defame him by saying that the FBI was in "disarray" and that Comey lost the trust of his top officials.

"Those were lies, plain and simple," he told the Committee.

President 'not a liar'

Comey also openly disputed Trump's account of their meetings, including the White House dinner. Previously, Trump had told the US media that Comey wanted to have dinner with him. The reason, according to Trump, was that Comey wanted to stay on as FBI chief.

He said the statement was "untrue," adding that he never initiated the dinner where Trump allegedly asked him for his loyalty.

Trump spokeswoman Sarah Huckabee Sanders defended the president during an off-camera briefing in the White House.

"I can definitely say the president's not a liar and frankly am insulted by that question" she told reporters, commenting on the Senate hearing.

She also commented on Comey refering to possible tapes of his meeting with Trump, saying that she had "no idea" whether President Trump was taping their conversations. Jokingly, she added she would "try to look under the couch" for the tapes.

Comey stops short of accusing Trump of obstruction

The former FBI boss also praised Special Counsel Robert Mueller, who has been appointed to oversee the inquiry into the alleged ties between Trump's aides and Russia. Testifying before the Committee, he said he had "high confidence" that Mueller would "turn over all the rocks" and find out all necessary information before he is done with his inquries.

However, Comey refused to say whether he believed that Trump engaged into obstruction of justice, saying it was "Bob Mueller's job to sort that out."

Comey also said that he kept his conversations with Trump secret from the agents probing Flynn. If the agents knew about Trump's alleged pressure, it would have a "real chilling effect" on their work, Comey said.

McCain tries to shift focus

The Senate Intelligence Committee consists of both Democratic and Republican lawmakers, each of whom was allotted seven minutes to question Comey.

Arizona senator and a former presidential candidate John McCain also questioned Comey, but surprisingly focused his questions on the Hillary Clinton election campaign. McCain repeatedly expressed confusion as he attempted to establish a link between Hillary Clinton's emails on one side, and the alleged Russian ties with the Trump team.

Comey replied he was "bit confused" by the line of inquiry and dismissed the connection between the two.

Trump surrogates attack

Donald Trump's private lawyer, Marc Kasowitz, responded to Comey's testimony with a statement to the public.

Addressing reporters in Washington, Kasowitz claimed that Trump "never pressured" Comey and "never sought to impede" the Russia probe.

Kasowitz also denied that Trump told Comey "I need loyalty" or asked him to "let go" of Michael Flynn.

The attorney also accused the ex-FBI boss of "surreptitiously and unilaterally" leaking "privileged" information to the press.

"We will leave it to the appropriate authorities to determine whether these leaks should be prosecuted," Kasowitz said, while also focusing on Comey's statement that Trump himself was not under FBI investigation.

"As he said yesterday, the president feels completely vindicated and is eager to continue moving forward with his agenda with this public cloud removed," Kasowitz said.

Republican congressman and speaker of the US House of Representatives, Paul Ryan, told the press that Trump "probably did not know" about protocols regulating the ties between the FBI and the White House.

"The president is new at this," Ryan told reporters. "He is learning as he goes."

"I'm not saying it's an acceptable excuse. It's just my observation."