BEIRUT, Lebanon - Syrian authorities have charged a U.S.-born Syrian blogger with trying to incite sectarian strife, activists said Tuesday, while regime forces fired on a funeral procession in a restive northwestern region, capping a bloody day of attacks that left at least 28 people dead.

Razan Ghazzawi is the latest among dozens of activists, journalists, and bloggers who have been detained since the revolt against President Bashar al-Assad began nine months ago, triggering a brutal crackdown that the United Nations estimates has killed more than 5,000 people and put thousands into security lockups.

Ghazzawi, 31, had been documenting human-rights abuses in recent months. She was arrested Dec. 4 at the border while en route to Jordan for a conference on press freedoms.

Syrian authorities charged her Monday with trying to incite sectarian strife, spreading false information, and weakening national sentiment - a charge often leveled against those who challenge the regime, according to rights activists. The charges could carry a prison sentence of up to 15 years.

The Syrian Center for Media and Freedom of Expression in the Arab World, where Ghazzawi worked, said in a statement Tuesday that she denied all charges. It demanded her "immediate and unconditional release . . . as well as an end to her trial and the annulment of the completely baseless charges."

Despite growing international pressure on his regime, Assad has forged ahead with his crackdown, unleashing security forces and the army on cities to crush an uprising inspired by similar revolts across the Arab world.

On Tuesday, regime forces fired on thousands of people taking part in a funeral procession in the northern city of Idlib, killing two people and pushing the day's death toll to at least 28.

The flareup of violence near the Turkish border is fresh evidence that the Syrian uprising is growing into a full-fledged insurgency.

Military defectors known as the Free Syrian Army have recently been fighting back with increasingly sophisticated attacks, giving many protesters hope of a fighting chance against Assad's fiercely loyal forces, but also complicating an uprising that was once largely peaceful.

The United States, European Union, and Arab League have imposed economic sanctions on Syria, and Washington and its Western allies are pushing for U.N. sanctions as well.