An MP who represented Zaidi Shiite rebels known as Huthis at a national dialogue was assassinated on Friday in the Yemeni capital, an official from his group told AFP.
"Two armed men opened fire on MP Abdel Karim Jadban as he was leaving a Sanaa mosque," said Abdel Karim al-Khaywani from the Ansarullah (Partisans of God) group.
He said Jadban died of his wounds before reaching hospital.
The murder comes as Huthi rebels have fought deadly clashes against hardline Sunni Muslim Salafists in the town of Dammaj in northern Yemen, where Shiites make up a majority in the mainly Sunni country.
A ceasefire was arranged by the presidency and parliament this week for the army to separate the two groups which have battled sporadically since the end of October.
On Wednesday, the editor of a newspaper close to Ansarullah and two passers-by were wounded in a bomb attack, also in the capital.
"These attacks target the forces of change in Yemen and are being carried out by the centres of traditional power," Khaywani said, without elaborating.
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Yemen is the only Arab Spring country in which a popular protest movement in 2011 led to the negotiated ouster of a long-time president, Ali Abdullah Saleh.
Under a transition plan, an all-party national dialogue aimed to draw up a new constitution by September 18 to clear the way for elections.
But the target date has been held up by several obstacles, especially southern demands for autonomy.
The dialogue is brokered by UN special envoy Jamal Benomar, whose office on Friday issued a denial that he had also been the target of an assassination bid.
"Shots fired as Mr Benomar was passing through the centre of Sanaa were celebratory shots for a wedding in the area, and he was not targeted," his office said.
The UN envoy said Tuesday that President Abdrabuh Mansur Hadi could stay in power after his term ends in February 2014 because of delays in implementing the transition deal.
Hadi was elected for a two-year interim period in February 2012, after Saleh signed a power transfer deal bowing to a year-long uprising against his 33-year rule.
"The power transfer agreement signed in November 2011 states that the transition period ends when all its milestones are completed," Benomar said.