Dozens of members from the April 6 Youth Movement clashed with security forces in front of the residence of Egypt's Prime Minister Hisham Qandil.
The clashes on Monday night started when Mohamed al-Assad, an April 6 member, allegedly threw a Molotov cocktail at a police truck belonging to the Central Security Forces (CSF).
The truck has been stationed outside the PM's residence in the Dokki suburb of Giza for security reasons.
April 6 members earlier gathered in front of Qandil's house in solidarity with a sit-in that had already been staged for one week by post-graduates protesting against unemployment.
A security official told Al-Ahram Arabic news website that security forces put out a fire that erupted in front of Qandil's home and that Assad was arrested that night.
Mohamed Kamal, another member of April 6, denied Assad's responsibility for throwing the Molotov cocktail, claiming it was hurled by an infiltrator or thug hired at the scene.
Besides Assad, at least 12 other post-graduates involved in the one-week sit-in were also arrested.
Qandil had announced that 66 government institutions would soon be announcing vacancies for holders of Masters Degrees and PHDs.
Protestors claim that Qandil refused their demands and riot police were dispatched to disperse the sit-in.
According to official statistics given by CAPMAS, at least 3.4 million Egyptians have been given unemployment status in the second half of 2012.