Unknown assailants have attacked a residential building of the International Committee of the Red Cross in the Libyan port city of Misrata, the agency says.
It said grenades and rockets were among the weapons used, causing major damage.
The agency said the attack meant it was forced, "with considerable regret", to suspend its work in Misrata and the eastern city of Benghazi.
It said the attack was the fifth in the two cities in three months.
"We are appalled by this latest act and by the deliberate targeting of our staff: they have put their lives at risk to serve the Libyan people both during and after the conflict," said Ishfaq Muhamed Khan, ICRC delegation head in Libya.
Seven staff were said to be inside the building at the time of the attack, but no-one was hurt.
They have now been withdrawn to the Libyan capital, Tripoli.
A month ago Libya recently held its first national polls since the demise of former leader Col Muammar Gaddafi, but regional and social tensions still regularly erupt into violence.