Razan Ghazzawi, 30, is the latest among scores of bloggers and journalists arrested since the break out of street protests against President Bashar al-Assad.
"She was arrested as she presented her passport to immigration at the Syrian border post of Nassib to cross to Jordan," one of her friends told Reuters.
Ghazzawi's last posting on www.razanghazzwi.com reported the release of fellow blogger Hussein Ghreir, freed last week after 37 days in jail.
Ghazzawi said Ghreir was lucky because he had spent most of his incarceration in a regular jail, compared to detention at secret police dungeons, home to "the worst kinds of torture."
There was no comment from the Syrian authorities, who have barred most independent journalists from the country, saying that non-state media have been spreading lies about the uprising, which they blame on a foreign conspiracy.
(Reporting by Khaled Yacoub Oweis, Amman newsroom)
Posted by Jason Lomberg, Technical Editor