An uneasy calm prevailed in the Yemeni capital late Tuesday after Vice President Abed Rabbo Mansour Hadi's negotiated cease-fire halted three days of clashes that have killed more than 70 people and wounded hundreds more.

Both government forces and dissident troops vowed to stand by the truce. The dissident troops are loyal to Ali Mohsen al-Ahmar, a top general who defected to the opposition in March.

Earlier Tuesday, at least 23 people were killed in Sana'a as the fighting intensified and spread to sensitive areas of the capital before the cease-fire took hold after nightfall. The clashes have forced thousands of civilians to flee Sana'a for the relative safety of rural areas.

The United States Tuesday condemned the violence and called on all parties to exercise restraint.

Yemen's youth-led protest movement stepped up demonstrations last week, angry after President Ali Abdullah Saleh instructed his deputy to negotiate a power-sharing deal. Many called the move the latest of the president's delaying tactics as he avoids demands to step down.

Diplomats and Yemeni politicians are trying to revive a long-stalled transition plan under which Mr. Saleh would hand over power. U.N. envoy Jamal bin Omar and the secretary-general of the six-nation Gulf Cooperation Council arrived in Sana'a Monday to boost efforts to get the deal signed.

Mr. Saleh has agreed to the GCC proposal three times since April. However, in each case, he has backed out before a deal could be signed. Yemen's president, in office for 33 years and a staunch U.S. ally, has clung to power despite tens of thousands demonstrating near daily since February to demand his ouster.

State Department spokeswoman Victoria Nuland reiterated that Washington supports “the Yemeni people's aspirations for a peaceful, orderly transition.”

The U.S. has trained and equipped several elite Special Forces units within the pro-Saleh Republican Guards. Yemen is home to one of the world's most dangerous al-Qaida branches, whose militants have staged or inspired a series of attacks on U.S. territory.

The chaos in the impoverished Gulf Arab nation already has allowed al-Qaida-linked militants to capture and hold a string of towns in Yemen's nearly lawless southern regions.

The International Organization for Migration says Yemen's violence over the past few days has complicated efforts to evacuate several thousand mostly Ethiopian migrants who are stranded near the Saudi border with Yemen.