The International Committee of the Red Cross said seven members of its staff were attacked, but unharmed, by armed gangs in Misurata. The organization said the attack marked the fifth time in three months that its staff members were attacked there or in Benghazi.
Ishfaq Muhamed Khan, the head of the ICRC's delegation in Libya, said the aid group was "appalled" by the attack and "extremely concerned" about escalating violence in Libya.
"Given the circumstances, we are forced to announce, with considerable regret, that we will be suspending all our activities in Misurata and Benghazi and that our delegates in those cities will be temporarily relocated," he said in a statement.
The European Union last month praised Libya for embracing democracy in the aftermath of the country's civil war.
Libyans recently voted in their first election in a generation. The U.N. mission in Libya said it estimated 2.8 million of the estimated 3.4 million registered voters cast their ballots for members of the National Congress.
The European Union, however, expressed concern about human rights violations in the country since Moammar Gadhafi's government collapsed last year. Violence was reported in parts of the country before the vote in July.