Huge crowds in Sanaa and other Yemeni cities have demanded that President Ali Abdullah Saleh leave after months of unrest.
But in a defiant speech to thousands of flag-waving supporters in the Yemeni capital today, Mr Saleh declared: "We will confront a challenge with a challenge."
Three people were killed and 15 wounded when troops shot at protesters in Ibb, a city south of Sanaa, medics and witnesses said. Demonstrators then set fire to an armoured troop carrier. Gunfire wounded three protesters in Yemen's third city, Taiz.
The latest killings pushed the overall death toll since protests began to at least 170.
Mr Saleh, a wily political survivor, has clung to power despite defections from politicians, army officers and tribal leaders.
Armoured vehicles, troops and even military academy students with batons deployed in Sanaa to contain a sea of protesters stretching 7km down a main street in Sanaa.
"We are steadfast, you leader of the corrupt," anti-Saleh demonstrators chanted. "Peaceful, peaceful, no to civil war."
Protesters in Sanaa, Ibb, Taiz and Hudaida held funeral processions for some of the 13 protesters killed on Wednesday.
In Sanaa, six coffins were taken to graves strewn with red roses. Some protesters held signs saying: "We won't be silent over this regime's crimes. The blood of martyrs is not cheap."
In Ibb, several military policemen joined in a funeral procession for a man shot dead in Wednesday's unrest.
Mr Saleh, addressing his supporters, denounced opponents as saboteurs and said they should use the ballot box instead.
"You are not using the same restraint (as we have). We don't cut roads, we don't cut gas lines in Maarib - this is the property of the people," he said. "It is the people's wealth. They eat from it and drink from it. Stop playing with fire."
International alarm has mounted over instability in Yemen, home to an ambitious wing of al-Qaeda, whose leader has sworn vengeance for the killing by US forces of Osama bin Laden.
"The United States is deeply concerned by recent violence throughout Yemen, and joins European Union High Representative (Catherine) Ashton in strongly condemning these troubling actions," state department spokesman Mark Toner said.
Mr Saleh offered a "constructive dialogue" with opposition parties, but did not promise to sign a Gulf Arab plan to which they have already agreed. Under the proposal, Mr Saleh would step down in 30 days, rather than when his term ends in 2013.
The deal mediated by the six-nation Gulf Cooperation Council (GCC) had angered many of the youthful protesters because it would shield Saleh and his entourage from prosecution.
The United States and its European allies urged all parties to sign and implement the agreement, but GCC member Qatar pulled out yesterday, citing "stalling...and lack of wisdom."
Reuters