London (CNN) Julian Assange tried to warn the US government that sensitive documents were to be leaked "imminently," but was told to call back in a few hours, according to his lawyers during the second day of the WikiLeaks founder's extradition hearing in London.

Assange personally warned the State Department that an encrypted database of 250,000 unredacted US diplomatic cables was about to be leaked in 2011, his lawyer Mark Summers told Woolwich Crown Court on Tuesday.

The cables included the identities of people -- some deemed high risk -- who had been in communication with the US.

Assange contacted officials after it became known that German newspaper Der Freitag had discovered the password to a database containing the unredacted files, Summers said.

An illustration of Julian Assange, centre, in the dock with his defence team Monday.

The 48-year-old Australian, along with WikiLeaks editor Sarah Harrison, telephoned then-Secretary of State Hilary Clinton's emergency line to sound the alarm about the unredacted material, the court heard.

Assange personally warned: "I don't understand why you're not seeing the urgency in this... people's lives are at risk," according to Summers.

But he was told to call back in a few hours, said the lawyer.

CNN reached out to the State Department for a response, but had not received one at time of publishing.

Extradition hearing enters second day

Assange's defense team hit back at allegations by lawyers for the US that he had deliberately put lives at risk by publishing the diplomatic cables in an unredacted form.

Tuesday's hearing is part of Assange's long-running battle against being sent to the United States for trial. The hearing began on Monday.

Assange was arrested on a US extradition warrant in April last year at the Ecuadorian embassy in London, where he had been living since 2012.

He now faces 18 charges in the US for his alleged role in encouraging, receiving and publishing classified documents linked to national defense. If convicted, he could be sentenced to up to 175 years in jail.

On the opening day of the hearing, lawyers for the US government argued that Assange had put the lives of sources and informants in "immediate" danger, and damaged the capabilities of US forces carrying out operations abroad.

But on Tuesday, Assange's legal team hit back at what it said were the prosecution's "lies." Lawyer Summers said that "far from being a reckless, unredacted release," one of Wikileaks' media partners had published the password to the unredacted materials.

This "enabled the entire world to publish those unredacted materials," he said. "They circulated on the internet, not on the Wikileaks site, but on other sites."

Summers added that "the US government was involved in the redaction process."

He explained that WikiLeaks -- which partnered with media organizations around the world including the Guardian, the New York Times, Germany's Der Spiegel, France's Le Monde and El Pais in Spain -- had a procedure in place to identify and redact the names of individuals considered to be at risk.

Assange complains of prison treatment

Assange has been held at London's Belmarsh prison since last year. On Tuesday, his lawyers complained about the inhumane treatment they said had been meted out to him at the high-security facility.

Assange was handcuffed 11 times, stripped naked twice, and put into a series of holding cells at the prison, his lawyers said.

"Treatment of this nature could impinge on his ability to participate in these proceedings," defense lawyer Edward Fitzgerald told the court.

Supporters of WikiLeaks founder Julian Assange, hold placards calling for his freedom outside Woolwich Crown Court on Monday.

Judge Vanessa Barrister told the court that her powers were limited in relation to the prison service.

Meanwhile, chants of "free Assange" could be heard from protesters outside the court. Already this week, the high-profile case has attracted celebrity campaigners including British fashion designer Vivienne Westwood.

The latest chapter in Assange's legal battle is far from over, with the hearing expected to take several weeks.