At least five people are reported to have been killed in Yemen as armed men including security forces opened fire on demonstrators in the capital Sanaa.
It is not known how many are injured. The bodies of at least four of the dead were taken to a nearby hospital.
The protesters were said to have been demonstrating against a deal that guarantees President Ali Abdullah Saleh immunity from prosecution when he leaves power.
After months of protests bringing the country to the brink of civil war, many Yemenis celebrated the announcement that their leader had finally agreed to step down.
Under the agreement signed with opposition leaders at a ceremony hosted by the Saudi king in Riyadh, Saleh will immediately transfer his powers to his deputy, but will retain the title of president until a new head of state is elected.
The 69-year-old who has been in office for more than three decades has gone back on an agreement to quit on previous occasions.
He will be the fourth leader in the Arab world to be forced from power since the mass protests began.