JERUSALEM — Israel indicted two prominent activists from its Arab minority on Thursday for allegedly spying for the Lebanese militant group Hezbollah, deepening a case that has raised tensions with the country's Arab minority.

Both men denied the charges, the latest in a series of cases in which the government has accused Arab citizens of aiding Israel's staunchest enemies.

Israel's Shin Bet security service said Arab activist Amir Makhoul confessed to meeting with a Hezbollah agent in Denmark in 2008 and agreed to collect information for the Lebanese militia.

Israel considers the Iranian-backed Hezbollah, which battled Israel to a stalemate in a monthlong war four years ago and is believed to possess tens of thousands of rockets, one of the greatest threats to the Jewish state.

According to the Shin Bet, Makhoul gave his handlers contacts for Israelis the group could try to recruit. He also provided details, including addresses, about Israeli security facilities, the Shin Bet said.

Speaking to reporters outside a courthouse in the northern city of Haifa, Makhoul angrily described the accusations as "a balloon that will burst very quickly."

"This legal proceeding is invalid and I reject all the allegations against me," he said.

Adalah — an Arab legal center in Israel that is representing Makhoul — said he had confessed to false charges following "harsh interrogation methods" that included sleep deprivation and being handcuffed to a small chair in painful positions for many hours.

"All of these harsh conditions point toward illegal confessions to facilitate the process of convicting the accused," said attorney Abeer Baker of Adalah. Shin Bet officials had no immediate comment.

Makhoul, who leads an umbrella network for Arab advocacy groups, was arrested on May 6 but was prevented from speaking to a lawyer for 12 days, Adalah said. Israel imposed a gag order on the case, releasing only limited information until charges were filed Thursday.

A second Arab-Israeli, Omar Saeed, was indicted on lesser charges of contacting a foreign agent, and transmitting information to an enemy. Israel also prevented Saeed from speaking to a lawyer for 16 days after his arrest on April 24. He, too, denies all charges.

The cases highlight the deep mistrust that often runs between Israel's Jewish majority and its Arab minority, about one-fifth of the population.

Although they enjoy citizenship rights — unlike their Palestinian brethren in the West Bank and Gaza Strip — Israeli Arabs have suffered from decades of discrimination, high unemployment and poverty. A Palestinian uprising last decade, as well as wars against Hezbollah and Hamas, have added to the tensions.

Some in Israel consider them a potential fifth column that could threaten the Jewish state by working with its enemies in neighboring states.

In recent years, several Israeli Arabs have been arrested for spying for Hezbollah. One suspect, Arab lawmaker Azmi Bishara, fled Israel in 2007 after police charged him with passing information to Hezbollah agents during Israel's war against the Lebanese militia the previous year.

Hezbollah fired about 4,000 rockets at Israel during the 34-day war, while Israel bombed the group's strongholds in Lebanon. Israel believes the group has restocked its arsenal and upgraded its capabilities by obtaining more powerful, longer-range missiles from Syria.

The war killed around 1,200 people in Lebanon and 160 in Israel.