"Today, a very large meeting of terrorist groups and armed groups took place in Sirte, we know who they belong to. They have a plan proposed at the meeting to attack the Oil Crescent", the spokesman said.
The press conference was broadcast by Arab and Libyan television channels.
However, the chairman of Libyan National Oil Corporation (NOC) Mustafa Sanalla promised to do everything possible to continue oil production and ensure the safety of oil sector employees.
Libya has been suffering from unrest since 2011, when its long-time leader Muammar Gaddafi was overthrown and killed. The country is divided between two rival governments, with an elected parliament governing the country's east and the UN- and EU-backed Government of National Accord (GNA) ruling the west from Tripoli.
The situation escalated last week, when the LNA, backed by the eastern government, announced an offensive against Tripoli in a bid to oust what Haftar called terrorist forces from the city. In response, armed forces loyal to the GNA started a military operation against the LNA on Sunday.