In a phone conversation on Thursday, the Iranian and Russian diplomats condemned the assassination of the Palestinian resistance leader.
Both sides underlined that politically-motivated assassinations were unacceptable while warning of dire consequences of such actions.
The organizers of such a provocative move seek to cause the ongoing process of talks between warring sides in the Gaza Strip to collapse, the two officials said.
For his part, Lavrov called on all influential parties in Gaza and in the Middle East to avoid actions that could lead to further regional instability and new casualties among civilians.
Earlier, the Foreign Ministry of Russia issued a statement, strongly slamming Haniyeh's assassination.
It is clear that the organizers of this political assassination were fully aware of the serious consequences of this threatening act for the entire region, it read.
There is no doubt that the assassination of Haniyeh will have an extremely negative impact on the course of indirect contacts between Hamas and the Israeli regime, within the framework of which mutually acceptable terms for a ceasefire in the Gaza Strip are being agreed upon, it added.
Russia in the statement urgently called on all parties concerned to exercise restraint and to refrain from steps that could lead to a dramatic deterioration of the security situation in the region and provoke a large-scale armed confrontation.
Haniyeh and one of his bodyguards were assassinated in their residence in the Iranian capital early on Wednesday.
Supreme Leader of the Islamic Revolution Ayatollah Seyyed Seyyed Ali Khamenei led a funeral prayer for Haniyeh on Thursday.
Haniyeh will be laid to rest in the Persian Gulf state of Qatar following another funeral prayer there on Friday.
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