(Adds general's comments, background)
By Ahmed Elumami and Ayman al-Warfalli
TRIPOLI/BENGHAZI, Libya, June 4 (Reuters) - Gunmen in Libya shot dead a Swiss national working for the International Committee of the Red Cross (ICRC), fired a grenade at the prime minister's office and tried to kill a renegade general in a series of attacks on Wednesday.
Anarchy is spreading in the North African oil-producing country where turmoil and political infighting have reigned since the 2011 uprising that ousted Muammar Gaddafi. A plethora of armed militias operate at will beyond state authority.
In the east outside Benghazi, ex-general Khalifa Haftar survived an assassination attempt. In Sirte, a central city where the government has little control, gunmen killed a Swiss ICRC official. And in the capital Tripoli, gunmen fired a rocket propelled grenade at the office of Prime Minister Ahmed Maiteeq.
"The Swiss head of a sub-delegation of the ICRC was shot dead by unknown gunmen while he was leaving a meeting in Sirte with another two ICRC members," said Salah Uddin, spokesman for the ICRC in Libya.
Nobody was hurt when the grenade hit the kitchen on the same floor as Maiteeq's office, an aide said, noting that the premier was not there at the time.
Maiteeq was elected by parliament last month in a chaotic vote that many lawmakers disputed. Outgoing Premier Abdullah al-Thinni has refused to hand over power, saying he wants to wait for a legal ruling on whether Maiteeq's election was legitimate.
In an attempt to reinforce his authority, Maiteeq took over the premier's office on Monday night, backed by a police escort.
Hours before the attack there, a suicide bomber blew up a sports utility vehicle packed with explosives at retired general Haftar's base in Benghazi, according to his spokesman, Mohamed El-Hejazi, and army officials.
Haftar survived but four men from his force were killed and 23 others suffered minor wounds, a medical source said.
Speaking later on television, Haftar said he had been treated with minor wounds in a hospital. "I am well," he told al Oula station. "There will be a strong response," he said, without elaborating.
His campaign to rid Libya of Islamists has triggered heavy fighting in Benghazi in the past few weeks, killing dozens of people.
Gaddafi's one-man rule and years of unrest since have left Libya with few functioning institutions and no credible army to impose state authority on former fighters and Islamist militants who often use military muscle to make demands on the state. (Reporting by Ahmed Elumami; Writing by Ulf Laessing and William Maclean; Editing by Mark Heinrich)