Rising tensions between the Taliban and the Islamic Republic of Iran boiled over on Saturday, with an exchange of heavy, Taliban-initiated gunfire breaking out along the latter's border with Afghanistan, as PBS NewsHour reports.

According to a number of reports, the most recent hostility – said to have killed three – stems from an ongoing water rights dispute between the nations that leaders on both sides have suggested could escalate.

Gunfire Exchanged

As PBS NewsHour noted, state-run media in Iran cited Gen. Quassem Rezaei in stating that the Taliban was the first to open fire on Saturday near the Afghan province of Nimroz.

According to Tehran's news agency, Iranian forces were ultimately able to inflict “heavy casualties and serious damage” in response to the aggression.

Taliban-controlled outlets, however, did not immediately acknowledge the outbreak of armed conflict.

Video footage posted to the Internet purported to show the situation on the ground, with the sparks of machine guns visible further afield, and regional advocacy group HalVash declared that “heavy weapons and mortars” were being used in the unrest.

Iranian Words of Warning

The violent exchanges come close on the heels of a warning from Iran to leaders of the Taliban against violating Iranian water rights related to shared use of the Helmand River, cautionary words on which the Associated Press reported earlier this month.

According to Iranian state media, the country's president, Ebrahim Raisi, pledged that his government would take all necessary steps to defend the nation's water rights as outlined in a treaty that dates back to 1973 and which determined the amount of water Afghanistan would be required to provide to Iran.

Raisi declared, “We will not allow the rights of our people to be violated,” and he implored Taliban authorities to heed his words carefully.

The Iranian president also expressed his wish that hydrologists from his country be permitted by the Taliban to conduct water level measurements of the Helmand River, as it has its point of origin in the Hindu Kush mountains in Afghanistan.

Resolution Elusive

PBS NewsHour noted that prior to the fighting on Saturday, Amir Khan Muttaqi, acting foreign minister for the Taliban, met with an Iranian envoy on the issue of water rights.

Iranian state media confirmed the meeting and suggested that outstanding concerns between the countries “will be better resolved through dialogue.”

However, as evidenced by the gunfire later that day – and also by recent pro-Taliban social media posts urging Taliban leaders to take a hard line against Iran – an easing of tensions is proving elusive.

Though it was Iran that seemed to fire the first verbal salvo in the latest phase of the water rights dispute earlier this month, the Taliban did not waste time in joining the fray over the weekend.

“We Will Conquer”

In the wake of Saturday's violence, the Taliban on Sunday adopted an aggressive stance with regard to Iran as the Jerusalem Post reported.

A video posted on Twitter showed Abdulhamid Khorasani, senior commander with the Taliban, declaring that his forces were prepared to do battle with the Iranians “with more passion” than they directed toward American forces in recent years.

“We will conquer Iran soon if Taliban's leaders give the green light for jihad,” the message warned.

According to the Post, some reports suggest that Iran has only been receiving roughly 4% of the water it is owed under the treaty's terms, and with upwards of 97% of its territory suffering from some degree of drought, it seems unlikely that Tehran will capitulate in this dispute anytime soon, despite the Taliban's tough talk.