Clashes again erupted Saturday between government troops and opposition tribal forces in the Yemeni capital Sana'a.
The fighting started when the government forces shelled the district of Hasbah in northern Sana'a, which is the stronghold of the dissident tribal chief Sadiq al-Ahmar, according to local residents.
There were no immediate details of casualties, DPA reported.
The violence comes hours before a security committee, formed under a United Nations-sponsored power transfer deal, was to meet on Saturday to plan the removal of barricades and gunmen from the streets.
Meanwhile, the UN envoy to Yemen, Jamal Benomar, has warned against hampering the implementation of the Gulf-brokered power transfer deal signed last month in Saudi Arabia.
Under the deal, President Ali Abdullah Saleh, who has ruled Yemen for 33 years, agreed to step down in return for immunity from prosecution.
"The UN Security Council is closely monitoring the ... process in Yemen," Benomar told reporters in Sana'a on Friday.
"The UN looks forward to seeing Yemen with its streets belonging to the people, not to militias and military groups," he added.
The impoverished Arabian Peninsula country has been gripped by anti-government protests since February.