The suicide attack, claimed to have been carried out by Jundullah - a militant Sunni Muslim group, killed at least 42 people in Pishin, a town in Iran's Sistan-Baluchistan province which borders Pakistan's own southwestern Baluchistan province.
The victims, according to Iran's state-run Fars news agency, included Gen. Nur-Ali Shushtari, the deputy commander of Iran's Revolutionary Guards ground forces, Gen. Mohammad-Zadeh, the Guards commander in Sistan-Baluchistan and at least three other commanders of Revolutionary Guards units.
Last month, an Iranian official speaking to CBS News on condition of anonymity accused Pakistan's security officials of helping Jundullah gain arms and training in Pakistan's Baluchistan community.
"We have told our Pakistani brothers a number of times that this kind of behavior will not help either of our two countries. You (Pakistan) must act before there is disaster," he said.
Jundullah has been accused by Iranian officials of operating out of Pakistan's Baluchistan region. In the past, Iranian officials have blamed Jundullah for several terrorist attacks on Iranian soil.
Iran is the only Muslim country with a Shia majority - making up about 90 percent of its population.
The two branches of Islam - Sunni and Shia - trace their differences to events following the death of the prophet Muhammad, when a group of Muslims joined ranks with Imam Ali-the prophet's son-in-law. This group came to be known as Shiyan-e-Ali or "friends of Ali," later shortened to just "Shia" Muslims, in contrast to the majority Sunni group.
The two provinces, Iran's Sistan-Baluchistan with a Sunni majority and Pakistan's Baluchistan with a mix of Sunni and Shia Muslims, have overseen close daily ties between people from both sides; Pakistani consumers routinely cross to the Iranian side to buy everyday commodities such as gas. Iran and Pakistan have discussed plans for years to set up an ambitious gas pipeline project from Iran to Pakistan's Baluchistan province, as a key channel for the export of Iranian gas.
But on Monday, a senior Pakistani government official warned that Iran was likely to tighten curbs along the largely un-policed border in response to the attacks.
"There is every possibility now of the Iranians increasing their aerial and ground surveillance along the border," said the official who spoke to CBS News on condition of anonymity.
In his strongest public criticism of Pakistan in recent times, Ahmadinejad said, "We have heard that certain officials in Pakistan cooperate with main agents of these terrorist attacks in the eastern part of the country." Ahmadinejad spoke following a cabinet meeting Sunday, according to Iran's state-run Press TV said;
Iranian officials have repeatedly accused British and U.S. intelligence of fomenting unrest in areas which are not Shia-dominated by arming militants from Jundullah. Western diplomats warned the timing of the latest Iran-Pakistan friction creates the danger of Pakistan losing its focus on fighting Taliban militants in the northern parts of the country.
On Saturday, Pakistan's military in the country's Waziristan region, close to the Afghan border, hoping to destroy key militant sanctuaries in the area.
"Growing tensions with Iran at this time are just not going to help" warned one western diplomat in Islamabad on Monday, speaking to CBS News on condition of anonymity.
"If Pak-Iran tensions grow, that will not help anyone. The danger will be of Pakistan loosing focus on Waziristan" he added.