Tonga's seaside capital Nuku'alofa is hosting the Pacific Islands Forum, with United Nations Secretary-General Antonio Guterres among the high-profile delegates.
Although the quake did not trigger a tsunami warning, some businesses near the coast briefly evacuated to higher ground.
The offshore tremor -- which struck at a depth of about 106 kilometres (66 miles) -- rattled buildings at the forum's newly built venue.
But it was soon back to business as usual in a city where earthquakes are relatively common.
Tonga sits atop the seismic Ring of Fire, an arc of intense tectonic activity that stretches through Southeast Asia and across the Pacific basin.
Huge swathes of the Tongan archipelago were blanketed in ash and pummelled by a tsunami after the immense Hunga Tonga-Hunga Ha'apai volcanic eruption of 2022.