A Tajik state TV broadcast incriminating Iranian officials for political assassinations in Tajikistan in the 1990s appeared to be the bluntest assertion of its kind between Dushanbe and Tehran.
But it follows a series of inauspicious moves that threaten to erode ties between two countries whose political and diplomatic relations have rarely matched their cultural and linguistic bonds.
At the heart of the latest tension is alleged Iranian support for the Islamic Renaissance Party of Tajikistan (IRPT), which was represented in the Tajik parliament for 15 years after a bloody civil war but was banned and branded a terrorist group in 2015.
Touraj Atabaki, a senior research fellow at the International Institute of Social History in Amsterdam, says Dushanbe's fresh claims should be seen against a "background of existing lack of trust."
"In its regional policies, Iran -- alongside warm relations with governments -- also tries to maintain relations with those governments' major opponents," Atabaki says.
String Of Killings
In a prime-time documentary aired on state television on August 8, the Tajik Interior Ministry claimed Iran fomented the 1992-97 civil war, provided financial assistance to the IRPT, and even trained militants linked to the party on Iranian soil.
A string of killings of prominent Tajik public figures in the wake of the war included the assassination of former parliament chairman Safarali Kenjaev in 1999.
The Iranian Embassy in Dushanbe told RFE/RL’s Tajik Service on August 9 that the ambassador was not present to comment, but that the embassy planned to probe the source of the "lies and slanderous" comments aired on state TV.
Iran and Tajikistan have close linguistic, cultural, and historical ties, and Tehran was among the first countries to establish diplomatic relations with Dushanbe after the collapse of the Soviet Union in 1991.
Iran, Russia, and the United Nations were mediators in the peace talks that ended the five-year war between the secular Tajik government and Islamist-led opposition forces.
Iran has also invested in major Tajik infrastructure projects, including a hydropower plant and a tunnel linking the capital with the country’s north. The two investments were reportedly worth around $200 million.
Rahmon Skips Rohani Ceremony
Yet Dushanbe has remained wary of Iran sheltering Tajik Islamic opposition figures and other government opponents in the 1990s and maintaining close ties with them ever since.
"Tajikistan suspects that Iran somewhat threatens the government of President [Emomali] Rahmon by actions that are not acceptable and appropriate in relations between two countries," Atabaki says.
Rahmon was not among the more than 100 foreign dignitaries who attended the August 5 swearing-in ceremony of Iranian President Hassan Rohani for a second term.
In April, Tajikistan was notably left out of a Central Asian tour by Iranian Foreign Minister Mohammad Javad Zarif.
In 2016, Tajikistan halted the import on Iranian food products, including poultry, cooking oil, and tea, citing their "low quality." Tajik authorities also said the Iranian products' labels were not in accordance with Tajik laws that require the ingredients to be listed in the Tajik language using the Cyrillic alphabet.
In July, the Transport Ministry publicly accused Tehran of violating the terms of a contract to build a key regional railway.
In 2016, Tajik authorities suspended the Tajik branch of the Imam Khomeini Relief Committee, a charity organization supported by the Iranian government.
Shokirjon Hakimov, a Tajik politician and analyst, traces tensions between Dushanbe and Tehran back to around the time of the arrest of a well-known Iranian billionaire in 2013.
"Relations between Tajikistan and Iran began to sour after the arrest of Babak Zanjani, an Iranian businessman who had invested in Tajikistan, who was later sentenced to death in Iran."
Zanjani was said to have been helping Iran sell oil during a period of international sanctions, but he was later accused of withholding billions of dollars in profits. An Iranian court sentenced him to death on corruption charges in 2016.
During his trial in Tehran, Zanjani, whose wealth was once estimated at around $13.5 billion, claimed that he had transferred some $2 billion to Tajikistan's National Bank. Local reports cited Iranian suspicions that Zanjani had used Tajikistan to move money out of Iran.
Tajik authorities have dismissed those claims and distanced themselves from Zanjani, whose financial empire in Tajikistan included a bank, an airline, and a bus terminal inaugurated by Rahmon himself.
Iranian actions with respect to the now-banned IRPT have engendered mistrust the other way.
Kabiri Visit To Tehran
In December 2015, just two months after the IRPT was banned and its leadership accused in Dushanbe of plotting to overthrow the government (the IRPT has rejected the charges as false), party leader Muhiddin Kabiri attended an Islamic conference in Tehran. Kabiri was seated next to an official Tajik delegation to the conference, and he was pictured being greeted by Iranian Supreme Leader Ayatollah Ali Khamenei, further angering Dushanbe.
Tajikistan's Foreign Ministry responded by sending a diplomatic note to Iran, protesting Tehran's decision to invite the "head of a terrorist party suspected of an attempted overthrow of the government."
The program that aired on Tajikistan's tightly controlled state television on August 8 described Kabiri as a "protege" of Iran and accused the IRPT of organizing the assassinations with Iranian instructions and financial support.
In it, a man who identified himself as a former Islamic fighter claimed he underwent sabotage training in Iran in 1995 along with 200 compatriots and returned to Tajikistan with instructions to kill prominent public figures. Neither his identity nor his claims could be independently verified.
Several well-known public figures, included a presidential adviser, a former grand mufti, a doctor, and an academic were killed between 1997 and 2004, as were 20 Russian officers.
With reporting by RFE/RL’s Tajik Service and RFE/RL's Radio Farda