In a statement late on Thursday, Iran's Foreign Ministry Spokeswoman Marziyeh Afkham pointed to the critical conditions in Yemen and the possibility of further violent acts by the opposition groups, saying that these groups are seeking to make the political process in the Arab country end in failure.
The Iranian spokeswoman also emphasized the necessity for exercising restraint and avoiding any violent move by the Yemeni parties.
She said the current problems in Yemen can be resolved through “Yemeni-Yemeni dialogues” with the participation of all political groups and parties.
Assailants on a motorbike on Wednesday shot dead Khaiwani, who is also an activist close to the Houthi group.
The group's television channel Al Maseerah said Al Khaiwani, who had served as a delegate for the group in a national dialogue conference on Yemen's future, was "martyred in a criminal assassination" near his house in the center of the capital Sanaa.
There was no immediate claim of responsibility, though Al Qaeda militants have claimed several previous attacks on the Houthis.