The deteriorating relations between Iran and Iraq worsened today with a revolutionary organization here claiming responsibility for an assassination attempt against a leading Iraqi official in Baghdad yesterday.

The fact that Iran's official Pars News Agency published a dispatch about the incident on the basis of an anonymous telephone call was seen here as an indication of the increasingly poisonous relations between the two Moslem neighbors.

The caller claimed that a militant of Iran's Fedaye Islam -- a right-wing Islamic guerrilla group -- was responsible for the attack on Tariq Aziz, Iraq's deputy prime minister and member of the ruling Revolutionary Command Council.

The Pars dispatch said that Iranian Samir Nour Ali had killed Aziz with a grenade and escaped unhurt. The Iraqi news agency reported, however, that the Iranian had been shot and killed by Aziz's body guards and that Aziz had emerged virtually unscathed.

The Fedaye Islam group is closely associated with Ayatollah Sadegh Khalkhali, the head of the revolutionary courts, which have sent hundreds of Iranians to their deaths in the past 14 months of revolutionary rule.

Khalkhali has long threatened that his organization will kill the deposed shah, and he has claimed responsibility for killing a son of the shah's twin sister, Princess Ashraf, in Paris last December.

Iran and Iraq each closed two of their provincial consulates late last year and last month recalled their ambassadors. Last week Iranian President Abol Hassan Bani-Sadr made an especially bitter attack against Iraqi President Saddam Hussein.

Bani-Sadr and other Iranian officials have become increasingly outspoken in their condemnation of alleged Iraqi involvement in rebel activity in the turbulent western boarder province of Kurdestan and oil rich Khuzestan in the southwest.

Iran charges that Iraq is backing sabotage of oil field installations and pipelines in Khuzestan and that arms are flowing into Iranian Kurdestan from Iraq.

Until Shah Mohammad Reza Pahlavi and Iraq reached a compromise in 1975 -- which has been falling to pieces with increasing speed since the February 1979 revolution here -- Baghdad bankrolled and armed several so-called liberation fronts in Arab-speaking Khuzestan and claimed it as the "lost province" of Iraqi Arabestan.

The 15-man Iranian National Security Council has met twice this week, reportedly to discuss the situation in Kurdestan. Bani-Sadr yesterday warned Kurds that if they did not put down their arms, the army would move in to reestablish order.

Since the Iranian revolution, Kurdestan had escaped effective central government control despite several unsuccessful efforts to pacify the mountainous region last summer. These were followed by an apparently fruitless effort to reach a compromise political solution.

Iranian Kurds are insisting that autonomy be written into the constitution.

Adding to Iranian concern were reports here that major Iranian opposition groups had recently met in Baghdad. Participants were said to include several former ministers under the shah as well as Shahpour Bakhtiar, the last prime minister under the monarchy and Lt. Gen. Gholan Reza Oveissi, an intimate of the deposed monarch and former ground forces commander and military governor of Tehran in late 1978.