Increasing violence in the Syrian capital is pointing toward a major fight ahead, a rebel spokesman told CNN Monday.

"The battle for Damascus is coming," said Abdulhameed Zakaria, a Syrian army colonel and doctor who defected and joined the opposition Free Syrian Army in Istanbul.

Video from the capital on Monday showed regime tanks in some streets and clashes with members of the opposition.

Video from activists in the central Damascus neighborhood of Medan showed people running and screaming amid loud sounds. It was unclear whether the blasts were gunshots or mortar fire.

Another video shows rebel fighters facing off against what appears to be a tank in the southern Damascus neighborhood of Tadamon, firing rifles, a heavy machine gun and a rocket-propelled grenade. They shoot at it repeatedly from behind a barricade down a rubble-strewn street, only to have a man tell them to stop wasting ammunition.

CNN cannot independently confirm the authenticity of the videos. Meanwhile, state-run TV showed a woman driving a car in Medan saying there was "nothing going on right now."

Asked about reports that there was shelling in Medan, she responded, "No, nothing is happening, thank God." But apparent gunfire could be heard in the background as she spoke.

With violence spreading throughout the country, the Red Cross announced that the conflict is a civil war throughout the country.

The declaration officially applies the Geneva Conventions to violence throughout the country. International humanitarian law now applies "wherever hostilities take place," the organization said Monday.

The Red Cross does not use the general term "civil war," and instead declares a "noninternational armed conflict." In April, the organization declared such a conflict in Homs, Hama and Idlib, but hostilities have spread enough that the conflict exists throughout the country, ICRC spokesman Sean Maguire said.