JERUSALEM, Oct 30 (Reuters) - An Israeli court sentenced a former soldier to four and a half years in prison on Sunday for leaking classified military documents to a newspaper, which later reported allegations of a policy to assassinate Palestinian militants.

Anat Kamm, 24, was convicted in February of possessing and distributing secret information, after striking a plea bargain with Tel Aviv District Court, where judges agreed in exchange to drop more serious charges of harming state security.

Kamm was found guilty of downloading 2,085 military documents on a disc during her army service and later passing some of this information to a correspondent for Israel's Haaretz daily, a court document showed.

The newspaper subsequently reported in 2008 that top army officers had authorised the assassination of Palestinian militants, in a possible violation of Israeli law.

Human rights groups have criticised Israel's policy of assassinating militant leaders since the early days of the last Palestinian uprising in 2000, especially when civilians were also killed. Israel has justified the practice as necessary to combat and deter potential attackers, while saying it has refined its methods to kill its targets more precisely.

A three-judge panel gave Kamm a 54-month sentence and an additional 18-month suspended term, the court document said, with judges writing that they had found "the motive behind taking the documents was mainly ideological".

Avigdor Feldman, one of Kamm's lawyers, said at the time she was convicted that she had "believed she stumbled onto (evidence of) war crimes."

Kamm, who has been under house arrest since late 2009, had faced a maximum sentence of 15 years, but the judges said they had taken into account that she had no prior offences and had cooperated with investigators.

Her case has sparked debate in Israel on the limits of press freedom in a nation where most men and women are subject to compulsory military conscription at 18, and go on to serve in the reserves, and many become privy to classified information.

Kamm was employed as a local journalist when she was arrested and disappeared from public view in late 2009, with military censors barring any publication of the case for months.

Journalists testified in her defence, some of them alleging she was being treated too harshly, noting how rarely, if ever, Israeli officials had been tried for alleged leaks of military documents to the press.

In summing up Kamm's sentence, the judges appeared to point at her case as a lesson to other soldiers. "The military establishment is built on the service of young, motivated people who fill complicated and secret roles," they wrote.

"If the army cannot trust the soldiers serving in various units and exposed to sensitive issues, then it cannot function as a regular army," they also said.