"The United States is deeply concerned by continuing reports of deaths and injuries at demonstrations throughout Yemen in the past week," State Department spokesman Philip Crowley said in a statement.
"We extend our deepest condolences to the families and friends of those who have lost their lives," he said.
He issued his statement amid reports that dozens of people were wounded Sunday in fresh clashes between anti-regime protesters and security forces in Yemen, as the death toll from weekend violence climbed to seven.
Pro-democracy opposition groups and students in Yemen have escalated their campaign to oust autocratic President Ali Abdullah Saleh after 32 years in power.
Witnesses said that police and loyalists of the ruling General People`s Congress party attacked protesters occupying University Square with live gunfire and tear gas, wounding dozens.
"People everywhere share the same universal rights to demonstrate peacefully and to freely assemble and express themselves. Violence must cease immediately," Crowley said.
"We call on the Yemeni government to quickly investigate these incidents and take all necessary steps to protect the rights of all its citizens, in accordance with President Saleh`s commitments."
"The current political impasse will be solved only when all parties engage in a process of peaceful negotiation and dialogue," the spokesman added.
"We reiterate our call for a commitment by all sides to participate in an open and transparent process that addresses the legitimate concerns of all Yemeni people and provides an orderly path to a nation that is more responsive to the political and economic aspirations of the people," he said.
"We believe this is the best approach to advance the interests of the Yemeni people."
Crowley`s statement comes just days after President Barack Obama`s top anti-terror advisor John Brennan urged Saleh to welcome his pledge to devolve power and urged the opposition to support the plan.
The call, the latest of a series of contacts between the White House and key anti-terror ally Yemen since a popular revolt erupted, followed a major concession by Saleh designed to end the political crisis.
Brennan reiterated that representatives of all sectors of the Yemeni opposition should respond constructively to President Saleh`s call to engage in a serious dialogue to end the current impasse, and said that the Yemeni government and opposition share responsibility for achieving a peaceful resolution of the crisis. (*)