Rights activists said Wednesday's violence across Syria killed at least 25 people, including eight Syrian troops who died in a retaliatory attack by suspected army defectors.

The British-based Syrian Observatory for Human Rights said the defectors ambushed a military convoy traveling through a village near the flashpoint city of Hama.

Hours earlier, rights activists said Syrian security forces opened fire on a car traveling through another nearby village , killing five civilians, while 12 others were killed by security forces elsewhere in the country.

The United Nations says more than 5,000 people have died since March, when the unrest first began. But Syria's U.N. ambassador has rejected that figure as “incredible.”

U.N. Secretary-General Ban Ki-moon told reporters in New York that “the status quo in Syria cannot go on.” “In the name of humanity, it is time for the international community to act,” he added.

In Washington, a congressional committee on foreign affairs examined U.S. policy toward Syria. Some members questioned whether the Obama administration should continue to advocate for a peaceful resolution in Syria in the face of widespread violence. Others echoed calls by President Barack Obama for Syrian President Bashar al-Assad to step down and end the killing, detention and torture of demonstrators.

Syria's uprising has turned increasingly violent in recent months, with defecting soldiers fighting back against the army and once-peaceful protesters taking up arms to protect themselves.