Residents of Hawaii and Russia’s Kamchatka Penninsula were warned of potential tsunami waves as a series of earthquakes, including a 7.4 magnitude one, struck off the Russian coast, according to the U.S. Geological Survey.

A Tsunami threat was issued off the Kamchatka coast, according to the U.S. Tsunami Warning System.

State and city officials in Hawaii also issued tsunami watches.

“Tsunami Watch Issued – Prepare to Act! A Tsunami Watch means a tsunami is possible, but the situation is still being evaluated,” the Honolulu Department of Emergency Management said in an alert posted on social media.

Those alerts followed the first of several notable quakes that hit within about an hour off the coast of Petropavlovsk-Kamchatsky, Russia, according to USGS.

The first was a 7.0 magnitude quake in the sea about 142 km east of the city, USGS said, citing preliminary data.

Within moments, a 6.7 magnitude quake struck some 130 km east of the city, followed by a series of quakes with magnitudes initially measured at 7.4, 6.7 and 6.6, according to USGS.

This is a developing story. Please check back for updates.