In an escalating war of words, a senior Iranian military official has said it is Iran's "inalienable and legal right to confront and destroy terrorists' dens in any depths of the neighboring country's soil, in case the Pakistani government takes no serious measure."

The statement comes days after the Iranian Chief of Army Staff warned of launching attacks against terrorist 'safe havens' operating along the Pak-Iran border.

Speaking to an Iranian news agency Fars, Lieutenant Commander of the Iranian Army, Brigadier General Ahmad Reza Pourdastan expressed his regret on what he observed was Pakistan's inability to curb terrorism.

"Unfortunately, the regions adjacent to Iran's eastern borders have turned into a shelter and place for training, preparing and equipping the terrorists who are mercenaries of Saudi Arabia and are supported by the US," he said.

Explore: Balancing act

On April 27, ten Iranian border guards were killed by militants in an ambush along the Sistan-Balochistan province. Iran said Jaish-al-Adl, a militant group, had shot the guards with long-range guns, fired from inside Pakistan.

Deepening the rift between the two neighbours, the Iranian police, in a statement carried on Iranian state media said “the Pakistani government bears the ultimate responsibility of the attack”.

The head of the Iranian armed forces then warned Islamabad that Tehran would hit bases inside Pakistan if the government does not confront militants who carry out cross-border attacks.

Pakistan's foreign office, which had expressed grief over the violent incident, today, summoned the Iranian ambassador to formally register its protest against the statement issued by Iran's army chief over the possibility of carrying out military strikes on Pakistani soil.

However, Iranian military officials seem adamant that Pakistan's role in maintaining peace along its border requires much more attention and vigilance.

Explore: Pakistan to deploy more troops on Iran border

“I ask the government of friendly and neighboring Pakistan, which this blind and cowardly act has taken place on their side of border, to take a responsible step and identify, introduce and punish members of the terrorist and Takfiri groups, who are behind this crime, as soon as possible," the brigadier said.

In 2014, Iran warned it would send troops to Pakistan to retrieve five Iranian border guards kidnapped by Jaish al Adl.

Pakistan said at the time that such action would be a violation of international law and warned Iranian forces not to cross the border.

Iran refrained from sending troops when a local cleric stepped in and resolved the situation.

Four of the guards were released a few months later, but one was killed by the militants.

Jaish al Adl is a militant group that has carried out several attacks against Iranian security forces with the aim of highlighting what they say is discrimination against minority groups in Iran.

The group claimed responsibility for attacks that killed eight border guards in April 2015 and 14 border guards in October 2013.