The Indonesian government had banned Islamic militants from travelling to the Middle East or elsewhere to fight Israel.
A police spokesman announced the measure after the self-styled head of the Jakarta-based ASEAN Muslim Youth Movement said more than 200 militants had been sent on missions to attack Israel's interests and countries that support the Jewish state.
Suaib Didu said last week that fighters had been trained to carry out suicide bombings to revenge Israel's military strikes on the Palestinian territories and Lebanon.
"We will prevent them from leaving. The government bans such travel," national police spokesman Anton Bachrul Alam said, adding there was no evidence anyone had left the country for the purpose.
Mr Alam said police in the West Kalimantan provincial capital of Pontianak had questioned Didu after he oversaw a rally by more than 200 volunteers said to be prepared to attack Israeli interests.
"He was not detained because what he did was just talk," Mr Alam said.
Militant groups in Indonesia, the world's most populous Muslim nation, have made claims in the past of sending volunteers to participate in conflicts overseas, which have often proved exaggerated.
Indonesia's foreign ministry said on Friday it would not advise volunteers to go to the Middle East and wage war against Israel, but it also could not stop travel of citizens in general.
The conflict in the Middle East showed no signs of letting up today, as Israeli air strikes killed 14 civilians in Lebanon while Hizbollah battled Israeli ground troops.
Indonesia has no diplomatic relations with Israel and historically has been a staunch supporter of the Palestinians.