Iran's Foreign Ministry summoned the Azeri ambassador on Sunday, accusing Azerbaijan of assisting Israeli intelligence in the assassination of an Iranian nuclear scientist blown up last month, Iran's Fars news agency reported.
Mostafa Ahmadi-Roshan was killed when two men on a motorcycle attached a magnetic bomb to his car on Jan 11. The thirty-two year old academic worked at the Natanz uranium enrichment facility in central Iran.
At least four scientists associated with Iran's nuclear programme have been assassinated since 2010 and a fifth was wounded in a bomb attack. Iran's Supreme Leader Ayatollah Ali Khamenei called Ahmadi-Roshan's killing a cowardly act and accused the United States and Israel of responsibility.
Iran says its nuclear programme is peaceful, but Western countries say it is aimed at building a nuclear bomb.
Israeli officials do not comment on whether they are behind the killings of Iranian scientists but have made clear they are pleased. Washington criticised the killing of Ahmadi-Roshan and denied blame.
The semi-official Fars news agency quoted the foreign ministry press office saying the Azeri ambassador, Javanshir Akhundov, was summoned because Azerbaijan had helped agents to get in contact with the Israeli intelligence agency.
According to the report, Akhundov was also rebuked over the mistreatment of Iranian officials in Azerbaijan and Iranian trucks having difficulties entering the country.
A spokesman for Azerbaijan's Foreign Ministry said he was not immediately able to comment on the report.
Azerbaijan, a secular Muslim former Soviet republic which borders on Iran, has friendly ties with the United States and Israel and has had difficult diplomatic relations with Tehran. Iran is home to a large ethnic Azeri minority.
Last month Azeri authorities arrested two men suspected of plotting to attack foreigners, including the Israeli ambassador in Baku and a rabbi.
Azeri authorities said the two suspects had been helped by an Iranian linked to Iran's intelligence services, who supplied them guns and explosives to smuggle from Iran.
Azeri authorities have also said they thwarted a plan by agents of Iran and Lebanon's Hezbollah militia to set off a car bomb near the Israeli embassy four years ago, and a plot targeting the U.S. and British embassies in 2007.
(Reporting by Hashem Kalantari in Tehran; Additional reporting by Lada Yevgrashina in Baku; Writing by Marcus George; Editing by Peter Graff)