Tens of thousands of government supporters and opponents took to the streets in the Yemen capital of Sanaa on Thursday.
The protests came one day after President Ali Abdullah Saleh's pledge to step down once his term expires. The Yemeni ruler has been in power for nearly 32 years.
Opponents of Saleh's regime, likely inspired by the turmoil in Egypt, want him to step down before his term ends.
"Thirty years of promises and 30 years of lies," one protest banner read. Protesters chanted: "Down, down with the regime."
But his supporters - some of who are state employees - claim the opposition is trying to "destabilize and create chaos."
Yemen, the base for al-Qaeda on the Arabian Peninsula, is viewed by the Obama administration as a key ally in America's fight against Islamic militants. Some fear the demonstrations will undermine a U.S.-supported crackdown on the terrorist group.
"Your government's efforts to disrupt al-Qaeda's operational planning and to deny it safe haven are profoundly in Yemen's own interests," U.S. Secretary of State Hillary Clinton told a public forum in Sanaa on Jan. 11.
"They have sought, more than once, to attack our country," she said. "Stopping such threats would be a priority for any nation, and it is a priority for us."