Protesters in Libya have attacked offices linked to the Muslim Brotherhood following the assassination of a prominent political activist.
Abdelsalam al-Mismari was shot dead as he left a mosque in Benghazi in eastern Libya after Friday prayers.
Demonstrators blaming the Brotherhood have taken to the streets.
They stormed offices of the Justice and Construction Party, the Brotherhood's political wing, in Benghazi and the Libyan capital, Tripoli.
A retired air force colonel and a senior police officer were also shot dead on Friday in Benghazi in the latest in a series of targeted killings of security personnel.
Libya's government is struggling to control armed groups nearly two years after Col Muammar Gaddafi was toppled.
There has been growing opposition to the increasing influence of the Justice and Construction Party (JCP) in the country's parliament.
Mr Mismari, a lawyer, was a vocal critic of the Brotherhood's presence in Libya.
He was one of the earliest organisers of protests that eventually led to the overthrow of Gaddafi in August 2011.
It is unclear who carried out the killing.
Protesters in Tripoli stormed the headquarters of the JCP and as well as those of the secular National Forces Alliance on Saturday, according to reports.
They smashed windows and looted furniture at the offices.
Demonstrators also attacked a building housing the JCP in Benghazi, the centre of the armed uprising in 2011.
"We want all political parties to be dissolved," Agence France-Presse news agency quoted one protester as saying.
"They're the cause of all our problems. First we need a constitution, then laws regulating political life before parties can begin operating."
Benghazi has seen a number of violent incidents since the fall of Gaddafi.
Radical Islamists were blamed for an attack on the US consulate last September in which the US ambassador and three other US citizens were killed.
The BBC's Rana Jawad in Tripoli said Mr Mismari's death represented the first assassination of an activist since the latest violence began.
Our correspondent says it marks a potentially dangerous turning point for the country. Some feel it is an attempt to silence civic groups, she adds.
In separate attacks on Friday, retired air force Col Salem al-Sarah was killed as he emerged from a mosque and police Col Khatab Abdelrahim al-Zwei was shot dead at the wheel of his car, officials said.