TEHRAN (Reuters) - Iran warned neighboring countries not to help its arch-foe Israel, one day after announcing it had rounded up a spy ring linked to Israel which it said had assassinated an Iranian nuclear scientist.

Israel has not ruled out military strikes on the Islamic Republic if diplomatic efforts fail to stop Tehran trying to build nuclear weapons. Iran has vowed to retaliate with missile strikes on Israel and U.S. targets in the Gulf.

“Our neighbors and the regional countries that have ties with the Zionist regime should know that any assistance given to this regime would be viewed as a threat to Iran,” Intelligence Minister Heidar Moslehi told a rare news conference on Tuesday.

“The regional countries’ interaction with this regime will help the creation of bases for terrorist and espionage actions.”

Iran said on Monday it had arrested a “network of spies” linked to Israel’s Mossad intelligence service which it blamed for the assassination of an Iranian nuclear scientist in 2010.

“The arrested cluster includes many networks ... so far, over 10 people connected to various networks have been arrested and arrests will continue,” Moslehi said. “They were all members of networks linked to Mossad.”

A remote-controlled bomb killed Tehran University scientist Masoud Ali-Mohammadi in Tehran on January 12 last year. Iran blamed the United States and Israel for the killing, a charge Washington rejected as “absurd”.

Western sources have said Ali-Mohammadi, a physics professor, worked closely with Mohsen Fakhrizadeh-Mahabadi and Fereydoun Abbassi-Davani, named in U.N. sanctions resolutions because of their work on suspected nuclear weapons development.

Another Iranian nuclear scientist was killed on November 29.

“MERCENARY GROUPS”

Iran said on Monday Israel had used “some European and non-European countries as well as some neighboring countries to carry out the assassination” of Ali-Mohammadi, without giving further details.

Israel has diplomatic relations with several Middle Eastern countries, including Egypt, Jordan and Turkey but is largely shunned by Arab and other Muslim states.

Tehran often accuses Israel and the United States of trying to destabilise the Islamic Republic, which has been hit by international sanctions for refusing to suspend its uranium enrichment-related activities.

“Mercenary groups like Rigi’s and PJAK ... had meetings with the Zionist regime to inflict blows on the Islamic Republic,” Moslehi said.

Iran sees PJAK, the Party of Free Life of Kurdistan which seeks autonomy for Kurdish areas in the country, as a terrorist group. The leader of Sunni rebel group Jundollah, Abdolmalek Rigi, was executed in 2010.

Iran and Israel have been arch-enemies since the 1979 Islamic revolution in Iran, and Tehran periodically announces arrests of people suspected of spying for Israel.

“We have documents and proofs that the Zionist regime has targeted Iran’s achievements and the nuclear field would not be an exception,” Moslehi said.

“This regime is opposed to any achievement in the region and all distinguished scientists in the Middle East are in danger.”

Under Iran’s penal code, imposed since the revolution, espionage can carry the death penalty and Iranians have been hanged for spying for Israel.

Israel, believed to be the only country in the Middle East with nuclear weapons, the United States and its allies accuse Iran of using a civilian nuclear programme as cover to build atomic weapons.

Iran denies the charge, saying it wants to use nuclear power to generate electricity.