According to court documents seen by AFP, Makhoul met Hassan Janna, a Lebanese-born recruiter for the Hezbollah militia, during a trip to Jordan in 2004.
The two remained in touch and in 2008, Makhoul agreed to help Hezbollah against Israel, it said.
Later that year, the documents say, he met another Hezbollah agent in Copenhagen who installed a communications programme on Makhoul's laptop computer through which he could send messages to the organisation.
It said Makhoul subsequently filed reports on the location of installations of the Shin Bet and Mossad -- Israel's domestic and foreign intelligence agencies -- an army base and the Rafael military industries.
Makhoul provided details on access and security arrangements at the Shin Bet headquarters in the northern port city of Haifa, it added.
Amnesty International said Makhoul's jailing was a "very disturbing development."
"Ameer Makhoul is well known for his human rights activism on behalf of Palestinians in Israel and those living under Israeli occupation. We fear that this may be the underlying reason for his imprisonment," it said.
"We are also extremely concerned by allegations that he was tortured and otherwise ill-treated following his arrest on 6 May last year in a dawn police raid on his home in Haifa."
Amnesty protested that Makhoul had not been allowed to see his lawyers for 12 days after the arrest and that a gag order had been imposed on media coverage of his case.
Makhoul, whose brother Issa is a former Arab-Israeli lawmaker, heads Ittijah (the Union of Arab Community-Based Associations), a Haifa-based group that fights discrimination against Israeli-Arabs.
He was arrested in early May 2010, shortly after fellow Israeli-Arab activist Omar Saeed was detained over similar allegations.
Charges against Saeed were reduced in a plea bargain and he was freed in September after serving a seven-month jail term.
Israel's 1.3 million Arab citizens, who make up 20 percent of the population, are Palestinians who remained in the country following the creation of the Jewish state in 1948, along with their descendants.
Hezbollah is blacklisted by Israel as a terrorist organisation.
In 2006, Israel and Hezbollah fought a devastating war that killed more than 1,200 people in Lebanon, most of them civilians, and more than 160 Israelis, mostly soldiers.
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The two remained in touch and in 2008, Makhoul agreed to help Hezbollah against Israel, it said.
Later that year, the documents say, he met another Hezbollah agent in Copenhagen who installed a communications programme on Makhoul's laptop computer through which he could send messages to the organisation.
It said Makhoul subsequently filed reports on the location of installations of the Shin Bet and Mossad -- Israel's domestic and foreign intelligence agencies -- an army base and the Rafael military industries.
Makhoul provided details on access and security arrangements at the Shin Bet headquarters in the northern port city of Haifa, it added.
Amnesty International said Makhoul's jailing was a "very disturbing development."
"Ameer Makhoul is well known for his human rights activism on behalf of Palestinians in Israel and those living under Israeli occupation. We fear that this may be the underlying reason for his imprisonment," it said.
"We are also extremely concerned by allegations that he was tortured and otherwise ill-treated following his arrest on 6 May last year in a dawn police raid on his home in Haifa."
Amnesty protested that Makhoul had not been allowed to see his lawyers for 12 days after the arrest and that a gag order had been imposed on media coverage of his case.
Makhoul, whose brother Issa is a former Arab-Israeli lawmaker, heads Ittijah (the Union of Arab Community-Based Associations), a Haifa-based group that fights discrimination against Israeli-Arabs.
He was arrested in early May 2010, shortly after fellow Israeli-Arab activist Omar Saeed was detained over similar allegations.
Charges against Saeed were reduced in a plea bargain and he was freed in September after serving a seven-month jail term.
Israel's 1.3 million Arab citizens, who make up 20 percent of the population, are Palestinians who remained in the country following the creation of the Jewish state in 1948, along with their descendants.
Hezbollah is blacklisted by Israel as a terrorist organisation.
In 2006, Israel and Hezbollah fought a devastating war that killed more than 1,200 people in Lebanon, most of them civilians, and more than 160 Israelis, mostly soldiers.
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