Iran has arrested 20 people it alleges are operatives of Israel’s Mossad spy agency in recent months, the judiciary said on Saturday, warning that they will face no leniency and will be made an example of.

On Wednesday, Iran executed a nuclear scientist named Rouzbeh Vadi, who was convicted of spying for Israel and passing on information on another nuclear scientist killed in Israel’s air strikes on Iran in June, state media reported.

Judiciary spokesperson Asghar Jahangiri told reporters in Tehran on Saturday that charges against some of the 20 suspects arrested had been dropped and they were released. He did not give a number.

“The judiciary will show no leniency toward spies and agents of the Zionist regime, and with firm rulings, will make an example of them all,” Jahangiri was quoted as saying by Iranian media.

He said full details would be made public once investigations were complete.

Executions of Iranians convicted of spying for Israel have significantly increased this year, with at least eight death sentences carried out in recent months.

Israel carried out 12 days of air strikes on Iran in June, targeting Iran’s top generals, nuclear scientists, nuclear installations, as well as residential neighbourhoods. Iran responded with barrages of missiles and drones on Israel.

Rights group HRANA reported 1,190 Iranian deaths during the 12-day Israeli attacks, including 436 civilians and 435 security personnel.

Israel said 28 were killed in Iran’s retaliatory attack.