A rare warning alert asking Seoul residents to "prepare to evacuate to the nearest underground shelter" on Wednesday left many confused as the text message didn't elaborate on where exactly they should go.

"Underground shelter" became one of the most-searched-for words online shortly after the warning alarm rang for North Korea's launch of a projectile that it claimed to be a military reconnaissance satellite at 6:32 a.m.

According to the Ministry of Interior and Safety, its National Disaster and Safety Portal offers information about over 17,000 shelters across the nation, including over 3,100 in Seoul.

If users put a specific location into the portal, the portal will compile a list of available shelters, officials said.

The government has also developed the Emergency Ready App both for Android phones and iPhone devices, which allows users not only to search for the nearest shelter, but also to receive location-based disaster alerts depending on the user settings of the app.

If users allow the app to keep track of the user's location, the app will provide you with the locations of shelters within a certain radius, ranging from 500 meters to 2.5 kilometers.

The most common shelters in Seoul can be found in some 300 underground stations, including metro stations as well as underground parking lots in apartment complexes, they added.