This comes as government forces and tribesmen slugged it out in the capital and demonstrators poured onto the streets of the impoverished country to demand that the President Ali Abdullah Saleh step down.
Saleh sustained a slight injury to the head in an attack on the mosque in the presidential palace, but he is fine, a senior government official told CNN. The president plans to address the media later on Friday.
Government spokesman Tareq al-Shami said Primeinister A Mli Mujawar, the parliament speaker, deputy prime minister, and the Sanaa governor were among seven injured.
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It was not immediately clear whether Saleh was among the seven Al-Shami mentioned.
Tribal fighters and the regime's forces in Sanaa had been battling with missiles.
The fighters shot missiles at the presidential palace and the government responded by launching missile strikes on a dissident tribal leader's property.
In Taiz, government security forces and gunmen protecting protesters fought street battles.
The security forces began shooting at protesters assembled in the city's Freedom Square, and gunmen supporting the demonstrators burned an armored vehicle belonging to security forces.
Abdullah Afti, a youth activist in Taiz, said four anti-government protesters had been shot during Friday prayers.
The White House called for "calm and restraint" and said the dispute between pro- and anti-government forces "must be solved through negotiations."
"We've seen the reports and are very concerned about violence in Yemen," White House spokesman Tommy Vietor said.
Fighting has rippled across Yemen for months between supporters of Saleh and anti-government forces who want him out of office. Discontent has rippled across the country and demonstrations have been common.
But late last month, battling between pro-Saleh forces and tribal elements added a new element to the instability in the country.
The International Crisis Group recently said that on May 23 fighting erupted between military forces controlled by "Saleh's son and nephews and fighters loyal to the preeminent sheikh of the powerful Hashed confederation, Sadiq al-Ahmar."
"The personal animosity and competition between the sons of the late Sheikh Abdullah bin Hussein al-Ahmar (Sadiq and his nine brothers) and the sons and nephews of Saleh have been a consistent obstacle to negotiations over a peaceful transfer of power. Now, this animus threatens to drag the country toward a full-scale civil war," the group said.
The fighting has focused on these groups but "it could easily escalate, drawing in other tribal factions" and the armed confrontation has already led to the deaths of more than 100 people, the ICG said in a "conflict risk alert" last Friday.
"During the course of a tribal mediation attempt, Saleh's security forces fired on Sadiq's home, killing several prominent sheikhs and injuring dozens of other individuals, including one of the president's closest allies and trusted negotiators, Ghalib Ghamish -- head of Political Security, Yemen's intelligence service," the ICG said.
The urban battles leave Sanaa's population "at great risk."
"Hundreds are fleeing, fearing a tribal invasion from the countryside," the ICG said.
While Saleh has been unpopular among many inside his country, he has been a longtime ally of the United States in the war against terror.
The United States has counted on his government to be a bulwark against militants, including al Qaeda in the Arabian Peninsula, but it believes he should transfer power in order to maintain stability in the country.
White House spokesman Vietor said that John Brennan, the president's homeland security adviser, just traveled to Saudi Arabia and the United Arab Emirates for meetings with government officials to "discuss options to address the deteriorating situation" in Yemen.
The Obama administration has been disappointed in Saleh's "continued refusal" to sign the Gulf Cooperation Council initiative.
The GCC, a coalition of six Gulf Arab nations, came up with a plan for a peaceful and orderly transfer of power that would lead to Saleh's departure.
"It's a very concerning situation. Violence is persistent over the past week or so, ever since President Saleh once again backed away from the table and decided not to sign what we believe was a very valid GCC agreement that really would chart a way forward," State Department spokesman Mark Toner said on Thursday.
"In that time, our ambassador there has consistently been in touch with the Yemeni government. And again, our efforts are trying to convince President Saleh that this agreement is the best way forward, it ... charts a path, if you will, for Yemen to move out of this period of crisis and to move towards a democratic transition."