Yemeni President Ali Abdullah Saleh ordered a probe into deadly violence in Sana'a on Thursday, a day after he agreed to an Arab League plan that calls for him to relinquish power.
Earlier Thursday, witnesses said five people were killed after loyalists to Saleh opened fire on protesters who were upset over a provision in his power transfer deal that gives him immunity from prosecution.
The state-run SABA news agency says Saleh condemned the violence and expressed regret that "forces and elements" in the country oppose peace and stability.
On Wednesday, Saleh and opposition leaders signed a long-awaited agreement that calls for him to transfer power to vice president Abed Rabbo Mansour Hadi. The plan, brokered by the Arab League, also calls for the government to hold early presidential elections.
The agreement is designed to end months of anti-government protests that have left hundreds dead and thousands wounded.
Also, al-Qaida-linked militants have seized control of several parts of southern Yemen as the government has struggled to contain unrest in other regions.
Some information for this report was provided by AFP and Reuters.