Authorities in Geneva have lowered the terror alert level raised earlier this month following intelligence about a specific threat in the Swiss canton, a statement said on Monday.

Geneva police on December 10 announced a manhunt for potential Islamic State group sympathisers and beefed up security at key locations, amid reports that US intelligence had identified a jihadist cell in the area.

The Geneva security services "have decided to return to the level of vigilance in force before December 10," a statement from the cantonal government said.

During the period of heightened alert, strategic locations were under round-the-clock watch, while the UN European headquarters, known as the Palais des Nations, had added security by UN guards.

Geneva security department spokeswoman Caroline Widmer told AFP that threats in the area were again being classified as "vague", after rising to "specific" levels three weeks ago.

During the period of heightened alert, two Syrians were arrested in Geneva after traces of explosives were found in their car.