Iranian Foreign Minister Mohammad Javad Zarif has accused Saudi Arabia of "actively" backing terrorist groups in western and eastern Iran.
Speaking on June 13 on the sidelines of a conference in Oslo, Zarif said Tehran has "intelligence that Saudi Arabia is actively engaged in promoting terrorist groups” in Iran's southeastern province of Sistan-Baluchistan, which borders Afghanistan and Pakistan and is home to a large Sunni population.
"On the Western side, the same type of activity is being undertaken," Zarif said.
Zarif's remarks came in the wake of deadly attacks on Iran's parliament and the tomb of Ayatollah Ruhollah Khomeini in Tehran on June 7.
Islamic State (IS) extremists claimed responsibility for the attacks, and Iranian officials have repeated accusations that Saudi Arabia funds Islamic militants, including IS.
The Sunni-ruled Saudi monarchy, Shi'ite Iran's regional arch-rival, denied involvement in the attacks.
Saudi Arabia, an ally of the United States, has long accused Iran of supporting terrorism.
Washington also accuses Iran of fomenting unrest across the Middle East and of backing terrorism.
At an Arab Islamic American Summit in Riyadh last month, U.S. President Donald Trump accused Iran of fueling "the fires of sectarian conflict and terror" and called for its international isolation.
Also last month, the Saudi mission to the United Nations accused Iran of "deception" and of "supporting terrorism and threatening stability in the region."
In a letter on May 17 to the UN Secretary-General and to the president of the UN Security Council, the mission said Iran violated international law through its practices and caused war crimes and crimes against humanity.
The letter said the Iranian Revolutionary Guards Corps is a tool that exports extremist Iranian ideology and spreads terrorism in the world by supporting extremist militias with arms, money, and people. It cited the militant Hizballah organization and sectarian militias in Iraq as an example.