TRIPOLI, Jan 25 (Reuters) - Four Egyptian embassy staff were kidnapped in Libya's capital Tripoli on Saturday, a day after another Egyptian diplomat was seized there by gunmen, the Libyan government said.

No group claimed responsibility for any of the abductions, but they came soon after a powerful Libyan militia reported its leader had been arrested in Cairo and threatened to retaliate.

"Four more have been kidnapped. One of them is the cultural attache and the other three are staff," the Libyan Foreign Ministry spokesman said, without going into further details.

Two years after Muammar Gaddafi's fall, Libya is still in flux with the government struggling to control heavily-armed former rebels, militias and Islamist militants who fought in the uprising but often challenge Tripoli's authority.

One militia group, the Operations Room of Libya's Revolutionaries, said on Friday its leader Shaban Hadia had been arrested in Egypt, where he had been travelling with his family for medical treatment.

Another of the group's leaders, Adel al-Gharyani, denied it had kidnapped the first Egyptian diplomat. But he called on Egyptian authorities to release their commander or there would be a "strong response" from the group.

A number of foreigners have been abducted and attacked in recent weeks. Libyan security forces earlier this week freed a South Korean trade official who had been held for days by kidnappers who authorities said were not politically motivated.

An American teacher was shot dead in Benghazi in December, and in January, a British man and a New Zealand woman were killed on a beach in western Libya.

The Egyptian government said on Friday that talks were ongoing to try and secure the release of the first diplomat, an administrative attache. (Reporting by Ghaith Shennib; writing by Patrick Markey; Editing by Janet Lawrence)