JERUSALEM, April 20 (Dan Williams/Reuters) - Israel has arrested an Australian who tried to enter the country as a tourist, charging him with working for the Palestinian Islamist movement Hamas.

The April 17 indictment of Eyad Abu Arga, a copy of which was obtained by Reuters on Wednesday, appeared to be part of a wide-ranging and sometimes covert campaign by Israel to curb Hamas, with which it has regularly clashed in the Gaza Strip.

Israeli prosecutors said Abu Arga, 47, is a computer expert who also holds Jordanian citizenship and allege he was recruited by Hamas in Saudi Arabia and Syria to improve the group's capabilities in counter-surveillance and rocketry.

Using his Australian passport, Abu Arga flew to Tel Aviv on March 23, tasked by Hamas with testing security standards at Ben-Gurion International Airport and gathering information about hi-tech conferences in Israel, the indictment said.

A lawyer for Abu Arga denied the allegations, saying he had been on a Mediterranean tour with his wife and, after being detained at the airport, made a false confession under interrogation by Israel's secret service Shin Bet.

He's not a Hamas operative. He didn't try to infiltrate into Israel, the lawyer, Lea Tsemel, told Israel's Army Radio.

Tsemel described Abu Arga as being of Palestinian Muslim descent and said his wife had been allowed to leave Israel.

Conviction for the listed charges -- membership in, and service of, an outlawed organization -- can carry lengthy prison terms in Israel.

Hamas declined comment. Australia's embassy in Israel referred queries to Canberra, which did not immediately respond.

In a separate case, a Palestinian engineer from Gaza who says he was abducted to Israel while visiting Ukraine in February has been charged with masterminding Hamas rocket projects -- allegations he denies.

Sudan, which according to Israeli authorities is a conduit for arms smuggled to Hamas-controlled Gaza through the Egyptian Sinai peninsula, blamed an April 5 missile strike which killed two people on Israel.

Israel declined comment on the incident, which mirrored an attack on a suspected smuggling convoy in eastern Sudan in 2009.

(Editing by Michel Rose and Paul Taylor)