The hacker who helped to expose Hillary Clinton's private email domain used during her time as US secretary of state has been jailed for more than four years.

Marcel Lazar, who used the alias "Guccifer", was sentenced to 52 months in a US prison after pleading guilty in May to charges including unauthorised access of a protected computer and aggravated identity theft after being extradited from Romania.

Lazar is believed to have hacked into email accounts of around 100 victims between 2012 and 2014. Those who had their accounts hacked include prominent figures such as former secretary of state Colin Powell, a relative of former president George W. Bush, and Sidney Blumenthal, a former Clinton White House aide and unofficial adviser to Clinton.

Lazar said in interviews he had breached the Democratic presidential candidate's private server at her home in Chappaqua, New York, but law enforcement and national security officials rejected the claim as meritless.

Lazar was arrested in Arad, Romania, in January 2014.