At least five protesters have been shot dead by loyalists of Yemeni President Ali Abdullah Saleh in the capital, Sanaa, reports say.
On Wednesday, Mr Saleh signed the deal in Saudi Arabia under which he is to step down after more than 30 years in power.
President Saleh agreed to hand power to his deputy after months of protests.
Many others were wounded in the clashes, reports say.
An AFP correspondent said the protesters were shot at by armed civilians whom they describe as Mr Saleh's "thugs", as they marched towards the city centre.
At least four bodies taken from the scene of the shooting were visible at a nearby hospital, correspondents say.
Thousands of people in Sanaa cheered the news of Mr Saleh's impending departure, but others rejected the agreement.
