Iran’s supreme leader has said Saudi Arabian authorities “murdered” Muslim pilgrims who were injured during last year’s hajj stampede, as Mecca prepares to host the annual event again.

“The heartless and murderous Saudis locked up the injured with the dead in containers — instead of providing medical treatment and helping them or at least quenching their thirst. They murdered them,” Ayatollah Ali Khamenei said in a statement on his website marking the anniversary of the disaster and calling for new management of the event. He offered no evidence to support the allegations.

Saudi Arabia’s crown prince and interior minister, Mohammed bin Nayef, said Iran was attempting to “politicise” the hajj.

In comments published later on Monday by the Saudi Press Agency, he said Iran had decided not to send its citizens to the pilgrimage this year, which starts on Friday. Iran accuses Saudi Arabia of sabotaging negotiations that took place earlier this year regarding the security of pilgrims.

The September 2015 stampede and crush of pilgrims killed at least 2,426 people, according to an Associated Press count. Tehran has said 464 of the dead were Iranian and blamed the catastrophe on Saudi mismanagement of the annual pilgrimage.

Khamenei has also blamed Saudi Arabia for an earlier crane collapse in Mecca that killed 111 people, and said the kingdom’s rulers had were “satans”.

“Those who have reduced Hajj to a religious-tourist trip and have hidden their enmity and malevolence towards the faithful and revolutionary people of Iran under the name of ‘politicising hajj’, are themselves small and puny satans who tremble for fear of jeopardising the interests of the Great Satan, the US,” he said in the statement.

A top Saudi official said Khamenei’s accusations reflect “a new low”.

“These accusations are not only unfounded, but also timed to only serve their unethical, failing propaganda,” said Abdulmohsen Alyas, the Saudi undersecretary for international communications and media at the Ministry of Culture and Information.

“Saudi Arabia stands ready to serve the pilgrims and ensure their safety and comfort,” Alyas said.

Iranian foreign ministry spokesman Bahram Ghasemi said the ministry has formed a committee to investigate the issue and pursue it in international forums, without elaborating.

The hajj stampede caused a new flare-up in tensions between Iran and Saudi Arabia, regional rivals that back opposite sides in the civil wars in Syria and Yemen. The two countries severed diplomatic relations in January after Saudi Arabia executed a prominent Shiite cleric and angry Iranian crowds overran Saudi diplomatic missions.

Saudi authorities have not released the findings of their investigation into the hajj disaster. Preliminary statements suggested the crush was caused when at least two large crowds intersected.

Saudi Arabia is this year issuing pilgrims with electronic bracelets and using more surveillance cameras to avoid a repeat of the crush.