TEL AVIV, Israel (AP) _ Mordechai Vanunu, charged with revealing Israel's nuclear secrets, claims he is being given food ''like a dog'' and plans to begin a hunger strike, a newspaper today quoted his brother as saying.

Vanunu, 32, a Moroccan-born Israeli, is charged with two counts of aggravated espionage and assisting an enemy in wartime. Israel is technically at war with most of its Arab neighbors.

Vanunu told his brother, Asher Vanunu, that he is being held in almost solitary confinement and will begin a hunger strike, according to the report in Haaretz. It did not say when he planned to begin his fast.

''They give me food like a dog. I'm confined 23 hours a day in a closed cell and they're trying to break me,'' Asher Vanunu, in an interview with the daily newspaper, quoted his brother as saying.

Asher Vanunu and the brothers' elderly parents, Shlomo and Mazal, visited Mordechai Vanunu on Sunday for the first time since his arrest last autumn.

The Haaretz report could not immediately be confirmed. Vanunu's lawyer, Amnon Zichrony, was not in his office today and his secretary refused to divulge Asher Vanunu's phone number.

Based on information provided by Vanunu, the London Sunday Times published an Oct. 5 story that said Israel had produced up to 200 nuclear weapons in a subterranean factory in the Negev desert and ranked sixth among the world's nuclear powers.

Mordechai Vanunu, who worked at Israel's Dimona nuclear plant for 10 years before being fired in 1985 because of budget cuts, told his brother his conscience would not allow him to remain silent about ''what is going on at the atom factory,'' Haaretz said.

Asher Vanunu said if a scientist in any other country had spoken out in warning because he did not trust the country's leaders, he would be considered courageous, said the newspaper.

''Motti (a contraction of Mordechai) is not a spy, just naive . .. and because he believes the country's leaders to be untrustworthy, he tried to awaken the Israeli people from their apathy,'' the newspaper quoted Asher Vanunu as saying.

Mordechai Vanunu disappeared from London on Sept. 30. In November, the Israeli government announced he was jailed in Israel but did not say how the technician was brought here.

When Vanunu was brought to the Jerusalem District Court to face charges in December, he flashed a message written on his hand implying he was abducted in Rome.

The Italian government has asked Israel for clarifications on whether Israel violated Italian law when he was brought to Israel.

Following the incident, Mordechai Vanunu's radio, books and newspapers were confiscated by prison authorities. Vanunu has appealed to the Supreme Court, demanding that his privileges be returned.