Ansar al-Sharia group said on Twitter that two of its fighters boarding a motorcycle shot dead Houthi leader Abdel-Karim al-Kheiwani on Wednesday afternoon in Sanaa.
It also said that the militants "safely" fled the scene following the shooting.
Leading Houthi member Mohamed al-Bekheiti had told The Anadolu Agency that al-Kheiwani had been gunned down at a street in Sanaa at around noon on Wednesday.
Yemen's Houthis emerged as a formidable political and military force last September when they assumed control of capital Sanaa before establishing control over other parts of the country as well.
Last month, the Houthis issued what they described as a constitutional declaration dissolving parliament and establishing a 551-member transitional council.
The declaration, however, was rejected by most of Yemen's political forces – along with some neighboring Gulf countries – which described it as a "coup against constitutional legitimacy."
Fractious Yemen has remained in a state of turmoil since pro-democracy protests forced autocratic president Ali Abdullah Saleh to step down in 2012 after 33 years in power.
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