"Saudi Arabia must not seek to bring baseless accusations against Iran with the intention of political gains and increasing tensions in the region," foreign ministry spokesman Bahram Ghasemi said.
"Iran has had no activity against international law and diplomatic principles in Saudi Arabia," he said, quoted by state news agency IRNA.
He said Riyadh had not passed on "any information to the Islamic Republic of Iran regarding the alleged Iranian person" reportedly among the accused.
A Saudi court earlier today condemned 15 people to death for spying for the Sunni kingdom's regional rival Iran, local media and a source close to the case said.
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The source told AFP that most of the 15 Saudis were members of the kingdom's Shiite minority.
Their trial opened in February, a month after Riyadh cut diplomatic ties with Tehran over the burning of the Saudi embassy and a consulate by Iranian demonstrators protesting the kingdom's execution of Shiite cleric Nimr al-Nimr.
Some of the defendants were accused of meeting Ayatollah Ali Khamenei, the supreme leader of predominantly Shiite Iran.
Two of the group were acquitted while the rest received jail sentences of between six months and 25 years.
Apart from one Iranian and an Afghan, all of the defendants were Saudis. The source said that one of the two acquitted was a foreigner.