AFP/Tripoli

Libya's toothless outgoing government admitted on Monday from its safe refuge in the east of the country that it has in effect lost control of Tripoli to armed militias.

The interim government led by prime minister Abdullah al-Thani, which resigned last week, said armed groups, mostly Islamist militias, were in control of ministries and blocking access to government workers.

"Ministry and state offices in Tripoli have been occupied by armed militias who are preventing government workers from entering and are threatening their superiors," the government said in a statement.

It said the interim government was in contact with officials and "trying to ensure the continuity of services from afar."

Libya has been sliding into chaos since Moamer Kadhafi was overthrown and killed three years ago, with interim authorities confronting powerful militias which fought to oust the veteran dictator.

The interim government announced last week it had tendered its resignation to the elected parliament, days after a rival Islamist administration was created.

The parliament and government are operating out of Libya's east for security reasons.

A rival body, the General National Congress, last week named pro-Islamist figure Omar al-Hassi to form a "salvation government".

Interim authorities have been steadily losing ground to the militias and the Fajr Libya (Libya Dawn) mainly Islamist alliance, which seized Tripoli airport on August 22 after weeks of fierce fighting with nationalist rivals.

On Sunday, Islamist militiamen moved into the US embassy compound in Tripoli that was evacuated in late July, with videos showing cheering men diving from an upstairs balcony into the facility's swimming pool.

Fajr Libya members said they had gone in to secure the complex of several villas in southern Tripoli, not far from the airport, to prevent it from being looted.

US Ambassador Deborah Jones, now posted in Malta, said on Twitter that there was no indication the complex had been damaged.

An AFP photographer who visited the complex spotted no damage apart from some shrapnel scars on an exterior barbed wire-topped wall.

"We have called on diplomatic missions to return to Tripoli, and, until that happens, we're here to secure the locations," said a militiaman posted at the US embassy.

Several foreign missions have fled in the face of growing insecurity in the capital.

On August 25, Thani, the prime minister, accused Fajr Libya militiamen, who hail mostly from the city of Misrata, east of the capital, of having ransacked and set ablaze his residence in southern Tripoli where the airport is also located.

- Deadlock -

A political transition has been stymied by the political deadlock pitting Fajr Libya against the internally-exiled authorities, which are operating from Tobruk, 1,500 kilometres (more than 900 miles) from the capital.

Fajr Libya rejects the legitimacy of the elected parliament because it allegedly supported air raids last month -- which US officials said were carried out by the United Arab Emirates -- against its fighters deployed at the airport before they defeated nationalist militia rivals.

Parliament has in turned branded Fajr Libya as terrorists, putting them in the same boat as the Ansar al-Sharia jihadists who control most of second city Benghazi.

The insecurity, as well as a lack of investment in upgrading rundown schools, have led to the start of the academic year, due on Sunday, being postponed in Benghazi, Misrata and Tripoli.