Yemen's Houthi movement pulled out of a meeting with the country's other main political and regional factions on a new constitution after its fighters abducted a top government official, sources close to the situation said.
Houthi gunmen seized Ahmed Awadh bin Mubarak, office director for President Abd-Rabbo Mansour Hadi in the capital Sanaa early on Saturday to stop him attending the meeting, which was to discuss a draft of the constitution, police sources said.
The movement's representatives then withdrew from the meeting, two other attendees said, showing how wrangling over the constitution threatens to intensify political turmoil and insecurity in a country with an active al Qaeda wing.
The Houthi militia, which controls Sanaa, has denounced leaked details of the draft, which President Hadi has said will ensure the country does not fragment into two regions based on the former states or north and south Yemen.
The draft is a result of a national dialogue, aimed at easing a transition of power following mass street protests that led former president Ali Abdullah Saleh to step down in 2012.
The details leaked to Yemeni media indicated the new constitution instead retains a plan for a federal state divided into six regions, which both the Houthis and southern separatists believe would weaken their power.
A powerful group of tribes backed by the party of Yemen's former president Ali Abdullah Saleh has also rejected the six-region plan, and urged the country instead be divided into much smaller governorates, analysts say.
Saleh's party, the General People's Congress, also walked out of Saturday's meeting on the draft of the constitution, the attendees said.
The situation in Yemen has become more chaotic since the Houthis, who demand more rights for the country's Zaydi Shi'ite Muslim sect, seized Sanaa in September and advanced into central and western parts of the country where Sunnis predominate.
Scores of people have already been killed in 2015 by al Qaeda attacks and clashes between the Houthis and Sunni militants and tribesmen.
The implications of further instability in the country were highlighted last week when it was revealed that participants in the attack on Charlie Hebdo newspaper in Paris had trained with al Qaeda in Yemen.