Gunmen killed Tuesday a key member of the Shiite Huthi rebels delegation to Yemen's reconciliation talks, while an Islamist party's representative was targeted by a car bomb, security officials said.
The attacks in separate areas of Sanaa came as delegates to the national dialogue convening for a final working session announced progress in the thorny talks that President Abdrabuh Mansur Hadi announced will finally end at a ceremonial session Saturday.
Ahmed Sharafeddin, a law professor, was shot dead as he drove from his house in Sanaa to the hotel where the talks are being held, a security official said.
He was attacked at a roundabout and died instantly, the official added.
Sharafeddin is the second Huthi representative to the talks to be killed since MP Abdulkarim Jadban was shot in a similar attack in November.
Shortly after the attack on Sharafeddin, a car bomb targeting the secretary general of the Al-Islah (Reform) party badly injured his son Omar Abdelwahab al-Ansi in another area of Sanaa, a security official said.
Abdelwahab al-Ansi leads his party's delegation at the reconciliation talks, but rarely attends sessions due to poor health.
"The attack was targeting the father but injured the son," a security official said.
The dialogue is part of a transition backed by the United Nations and the Gulf countries and saw president Ali Abdullah Saleh step down after 33 years in power following massive Arab Spring-inspired protests in the region's poorest country.
Delegates agreed Tuesday on a document on which a new constitution will be based in a future federal state.
Hadi will announce details on Saturday, ending divisions over the number of regions that will make up the future state. Some are pressing for two in the south and four in the north, while others want two large entities -- one northern and another southern.
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Delegates also agreed that Hadi's extended presidential term will end with the election of a new president, a process that could take years as it awaits a new constitution and electoral law.
A 17-member technical committee will be charged with drafting the constitution, which would then be put to a referendum but no time frame was announced.
Hadi will then have a year to hold general elections.
Yemen is the only Arab Spring country where an uprising resulted in a negotiated solution.
Hadi, who arrived at Tuesday's session after he heard of Sharafeddine's killing, told delegates in an impassioned speech that "the dialogue will continue, and evil forces will fail."
Some Huthi members walked out after receiving news of the killing.
The UN representative to Yemen, Jamal Benomar, also condemned the attack, slamming it as a "desperate attempt to jeopardise the dialogue."
Al-Islah also condemned the "cowardly terrorist crime" against Sharafeddine, which aims at "hampering the ending of the national dialogue."
It also called for "an urgent and transparent probe" into the attack.
Tuesday's attacks come against a backdrop of fighting between Huthis and powerful tribes, which has resumed in Amran province after a series of ceasefires brokered by the government halted months of combat in several northern areas.
The rebels, whose stronghold is the northern province of Saada, accuse the tribes, joined by armed supporters of Al-Islah, of backing hardline Sunni Salafists fighting the Huthis in the enclave of Dammaj since late October.
The town in Saada province has been besieged by the rebels for months.