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authorities have arrested several people over the assassination of a colonel in May that Tehran has blamed on Israel and its Western allies, judiciary spokesman Masoud Setayeshi said on Tuesday.

The Guards, Iran's elite security force, said the shooting of in the capital Tehran by two people on a motorcycle was the work of "terrorist groups affiliated with global oppression (West) and Zionism (Israel)".

"Several people have been arrested in the case of the assassination of martyr Khodai. The necessary legal orders have been issued for them and the case is under investigation," Setayeshi told a news conference, according to state media.

The Israeli Prime Minister's office, which oversees intelligence agency Mossad, declined to comment on the events in the Iranian capital.

Israeli media said Khodai headed a unit of the Quds Force - the Revolutionary Guards' overseas arm - that planned attacks on Israelis abroad.

Iran said Khodai was a "defender of the shrines", referring to military personnel or advisers who the Islamic Republic says fight on its behalf to protect ShiaÌýMuslim sites in Iraq or Syria against Sunni militant groups such as Islamic State.

Iranian forces have played a key role in support of Syrian President Bashar al-Assad, Tehran's ally, against Islamic State and other militant and rebel groups in Syria's civil war.

Khodai's killing came at a time of uncertainty over the revival of Iran's 2015 nuclear deal with world powers after months of stalled talks.

At least six Iranian scientists and academics have been killed or attacked since 2010, several of them by assailants riding motorcycles, in strikes believed to have targeted Iran’s uranium enrichment programme, which the West says is meant to develop a nuclear weapons capability.

Iran says its nuclear energy programme has solely peaceful purposes, and has denounced the killings as acts of terrorism carried out by Western intelligence agencies and Mossad. Israel has declined to comment on such accusations.