Activist Mahmoud Yassin added that Houthis had released 18 out of a total of 24 people they had detained earlier on Sunday during an opposition protest.
He told The Anadolu Agency by phone that a group of activists had started a sit-in in the Yemeni capital to put pressure on the Houthis to release the remaining six activists.
AA could not immediately obtain comments from the Houthi group on Yassin's remarks.
Earlier on Sunday, Houthis forcefully dispersed an opposition protest in Yemeni capital Sanaa and then kidnapped some protesters.
The move had angered several Yemeni parties, including the Socialist Party, which decided to halt dialogue with the Houthis in reaction.
The Houthis seized control of Yemeni capital Sanaa in Sept. of 2014 before moving on to establish control over other parts of the country as well.
The rise of the Houthis has pitted the Shiite group against local Sunni tribes and Al-Qaeda, the latter of which is said to remain active in Yemen.
Yemen has remained in the throes of turmoil since President Ali Abdullah Saleh stepped down in 2012 under pressure from a months-long popular uprising against his 33-year rule.