Kuwait's Foreign Ministry summoned Iranian Ambassador Mohammad Totonji on Wednesday and handed him a protest note over a statement issued by his embassy, which the ministry described as interference in the country's internal affairs.

The dispute centres on a Kuwaiti court ruling that sentenced three people, including an Iranian, to death on charges of spying for Iran and Lebanon's Hezbollah and plotting to assassinate state officials.

The ministry called the embassy's statement "a flagrant interference in the internal affairs of the State of Kuwait" and an infringement on its sovereignty and the independence of its judiciary, in clear violation of international laws and norms.

Deputy Foreign Minister Hamad Suleiman Al-Mashaan reiterated Kuwait's firm rejection of any interference in rulings handed down by national courts. He urged Tehran to abide by international law and the UN Charter, particularly the principles of good neighbourliness and non-interference, as well as the 1961 Vienna Convention on Diplomatic Relations.

Earlier in the day, the Iranian embassy had denied that any of its nationals was involved in an assassination plot or any act threatening Kuwait's national security, saying the person in question had not been in Kuwait in the past ten years.

On Monday, the State Security and Terrorism Criminal Court sentenced three defendants to death in a case that, according to Kuwaiti media, involved plans to assassinate senior figures including First Deputy Prime Minister and Interior Minister Fahad Al-Yousef. Eight others received five-year prison terms. Authorities have not disclosed the identities or nationalities of the 11 defendants.

Tensions between the two countries have risen since late February, when Tehran struck what it considered US targets in Kuwait. Kuwait condemned the attacks, saying they hit civilian sites and infrastructure.