Saudi Arabia and Iran have exported their bitter regional tussle to Rome, accusing each other of villainous meddling in the Middle East during diplomacy talks in the Italian capital.

"They have literally got away with murder in our region and the world," Saudi Foreign Minister Adel Al-Jubeir told a three-day conference on creating "a positive agenda" in the Mediterranean on Friday.

The gathering, called "Beyond Turmoil", became the stage for a bitter slanging match between the two countries, with Al-Jubeir saying Iran's "negative influence throughout the region" was clear to see.

Iran and Saudi Arabia are engaged in a regional battle for dominance being fought by proxies in Syria, Iraq, Yemen, Lebanon and other countries -- a tussle which has drawn in the West.

"Since 1979 Iran has been the world's chief sponsor of terrorism", Al-Jubeir said.

Tehran "harbours and facilitates the movement of terrorists" and "established Hezbollah in Lebanon, using it to launder money and smuggle drugs," he added.

Iran got its own barbs in first, with Foreign Minister Mohammad Javad Zarif saying on Thursday: "I don't want to turn this into a Saudi bashing, but..."

Saudi Arabia "has rejected every ceasefire effort in Syria, in Lebanon," he said.

"Who supported ISIS (the Islamic State group), hoping they would overthrow the government of Syria in three weeks? Who was behind an entire blockade of Qatar?

"Who tried to force the prime minister of Lebanon out of office?" he asked.

"We believe all the countries need to live together, work together, but some people are trying to exclude us," he said sadly.

Al-Jubeir protested that it wasn't Saudi Arabia that struggled to have friends and allies in the region and beyond and Iran might want to do some soul-searching.

"We have good relations with almost every country in the world, except Iran and North Korea. Who is Iran friends with apart from (Syrian President Bashar) al-Assad and North Korea?" he asked.

It fell to a tired-sounding Russian Foreign Minister Sergei Lavrov to urge the pair to try dialogue rather than insults.

"We have been raising the issue of Saudi Arabia and Iran differences many times, they should start talking. It's really unfortunate," Lavrov said.