UN Secretary General Ban Ki-moon on Monday strongly condemned the use of live ammunition in Yemen where loyalists of the president shot dead 52 people at anti-regime protests last week.
"I strongly condemn the use of live ammunition against demonstrators by security forces in Sanaa," Ban told reporters following talks with Arab League chief Amr Mussa in Cairo.
Tanks were deployed Monday across the Yemeni capital including at the presidential palace, the central bank and the ministry of defence, after a senior general defected to the opposition.
"The Yemen government has an obligation to protect civilians. I call for the utmost retraint and end to violence," Ban said.
"There is no alternative to an inclusive dialogue on political, social and economic reform to address Yemen's political crisis."
President Ali Abdullah Saleh on Sunday sacked his government after tens of thousands massed to bury many of those who were killed, the largest gathering of his opponents since protests against his regime erupted in January.