(CNN) -- The use of lethal force against peaceful demonstrators in Syria was deemed "unacceptable" Friday by the U.N. secretary-general.
Ban Ki-Moon said in a statement that he is "concerned about the reported killing of demonstrators" in Diraa, Syria.
Witnesses said riots erupted Friday in the Middle Eastern nation. It is the latest of a string of Arabic-speaking nations beset with discontent.
The unrest spread through Hims, Diraa, Banyaas, Der Elzour and the capital, Damascus, witnesses said, and there were claims of deaths and injuries, but the assertions could not be independently confirmed.
Calling it "the responsibility of the government to listen to the legitimate aspirations of the people," Ban urged Syrian authorities to refrain from violence and to abide by their international commitments regarding human rights, which guarantee the freedom of opinion and expression, including the freedom of the press and the right to peaceful assembly.
His comments were echoed Friday by the United States, which urged the Syrian government to "address the legitimate aspirations" of its people.
"The United States strongly condemns the violence that has taken place in Syria today and calls on the Syrian government to allow demonstrations to take place peacefully. Those responsible for today's violence must be held accountable," said U.S. National Security Council spokesman Tommy Vietor.
Demonstrators took to the streets to demand freedom and urge an end to corruption, but police surrounded hundreds of them and made arrests.
"Security forces are clearly nervous and did not expect to have demonstrations in five different places at the same time," a witness said.
A Facebook page that called for "Dignity Friday" showed images of clashes between protesters and security personnel.