* President has warned of "radicalisation" in Arab minority
* Netanyahu aide says IS risk less than in Western nations
* Sees Palestinian militants, Hezbollah as bigger threats
By Dan Williams
JERUSALEM, June 2 (Reuters) - Israel's crackdown on Arab citizens trying to join Islamic State in Syria or Iraq or to set up cells at home have prevented the threat reaching the scale seen in the West, an adviser to Prime Minister Benjamin Netanyahu said in a magazine interview.
About 18 percent of Israel's population are Muslim Arabs, many of whom identify with the Palestinian struggle, although they seldom take up arms against the majority Jewish country. br>
However, a rash of defections to Islamic State-held areas of Syria and Iraq and trials of Israeli citizens for identifying with the militant group prompted President Reuven Rivlin to warn in January that "considerable radicalisation" was taking root among Israel's Arab minority.
Eitan Ben-David, head of the Counter-Terrorism Bureau in Netanyahu's office, told the bi-monthly journal 'Israel Defense' that "more than a few dozen, but not more than 100" Israeli Arabs had joined Islamic State's ranks - and some might return.
"These foreign fighters can certainly pose a grave danger internally, so the Shin Bet (security service) and all the state system is doing very good work in foiling this threat, which could be a kind of spreading cancer," Ben-David said.
"To our satisfaction, the situation is reasonable. It is not like any European country, nor even America, or places like China or Russia which have had a great number of homegrown ISIS fighters," he said, using an acronym for Islamic State.
Israel formally outlawed Islamic State in 2014 and negotiated the repatriation for trial of several Arab citizens who had joined or tried to join the insurgents via Turkey or Jordan.
But government policy hardened last year after one Israeli Arab used a paraglider to fly into an Islamic State-controlled part of southern Syria and after another who had served as a volunteer in Israel's army defected to the insurgents.
Further raising alarm, two video clips surfaced in October in which Islamic State gunmen vowed in Arabic-accented Hebrew to strike Israel. The group's leader, Abu Bakr al-Baghdadi, echoed the threat in an audiotape released in December.
But Ben-David sounded circumspect about that prospect, citing potentially more pressing dangers from Lebanon's Hezbollah guerrillas or Palestinian militants.
In an incident on Thursday, a Palestinian woman tried to stab an Israeli soldier in the occupied West Bank and was shot dead, the military said.
In the last half year, Palestinian attacks have killed 28 Israelis and two visiting U.S. citizens. Israeli forces have shot dead at least 196 Palestinians, 134 of whom Israel has said were assailants. Others were killed in clashes and protests.
"When it comes to Islamic State, we worry about terrorist attacks against Israeli or Jewish targets, including abroad, but we are not a main target right now," he said.
(Writing by Dan Williams; Editing by Jeffrey Heller and Gareth Jones) ((firstname.lastname@example.org; +972)(0)(2 6322202; Reuters Messaging: email@example.com))