Foreign Minister Shaikh Mohammad al Sabah told the newspaper Al Qabas that Kuwait will expel three Iranian diplomats whose names were revealed in the verdict.
"The court ruling on Tuesday revealed the extent of the anti-Kuwait political, economic and military plots by the spy ring," he said.
"The court has also revealed the direct link between the ring and the Revolutionary Guards in Iran."
Three men were given death sentences Tuesday, two of them Iranians and the third a Kuwaiti, Gulf News reported. Two more, a Syrian and a stateless man, received life sentences, and an Iranian man and woman were acquitted.
Kuwait has also recalled its ambassador from Tehran for consultations and plans to lodge a protest with the top Iranian diplomat in Kuwait, the minister said.