Hassan al-Qahtani, a Saudi security official working at their consulate in Karachi, was gunned down in July about 200 feet from his office by a man on a motorbike. News reports at the time linked the killing to tension between Pakistan’s Sunni and Shiite communities.

But a Saudi official said Thursday that his country and the United States agree that Iran’s Quds Force was involved in the Karachi killing. That allegation, if true, adds important new detail to the portrait of an Iranian covert-action service that has been escalating its attacks against Saudi targets.

The Saudi official, reached by telephone, said that Pakistani intelligence had identified the killer as a member of a Shiite dissident group known as Sapih Mohammed, which has connections with the Quds Force. The Saudi official said this conclusion, that the group had links with Tehran, was based on messages between Iranian officials in Islamabad and members of the dissident group.

The Saudi official noted additional examples of Iran’s campaign against Riyadh and its allies. He cited the 2005 killing of former Lebanese prime minister Rafik Al-Hariri. A U.N. Special Tribunal charged this year that the murder was plotted by four officials of Hezbollah, the Iran-backed Shiite militia in Lebanon. The senior Hezbollah official among the four, Mustafa Badr al-Din, is viewed by U.S. counterterrorism analysts as having close links with the Quds Force.

As further evidence of the Iran-backed campaign, the Saudi official cited the threats against Saudi Arabia’s ambassador to Beirut, Abdel Aziz al-Khoja, who was forced to flee in 2008 after Hezbollah took to the streets in West Beirut and other parts of Lebanon.

The Saudi official also provided new allegations about Gholam Shakuri, the Quds Force official who was named in Tuesday’s indictment as having conspired with an Iranian American named Manssor Arbabsiar to murder the Saudi ambassador to Washington. He described Shakuri as an important Quds Force case officer who had helped organize militant Shiite protesters in Bahrain.

According to the Saudi official, Shakuri was among the Iranians who met Hasan Mushaima, a radical Bahraini Shiite cleric, during a stopover in Beirut last February, when Mushaima was on his way back home to lead protests in Bahrain.

A cautionary note: These are all just allegations, and raw intelligence sometimes leads to hasty conclusions. But the additional evidence does address the central puzzle of the Washington assassination plot, which is why a sophisticated organization like the Quds Force would take so many risks to go after the Saudis, and use such unlikely proxies. Answer: They’ve done it before.