Hundreds of pagers carried by Hezbollah members blew up nearly simultaneously in an attack that tops a series of covert assassinations and cyber-attacks in the region.

Bulgaria and Norway became new focal points on Thursday of a global hunt for who supplied Hezbollah with the thousands of pagers that exploded in Lebanon this week in a deadly blow to the militant group.

By Ben Blanchard and Faith Hung TAIPEI (Reuters) -Authorities in Taiwan and Bulgaria on Friday denied involvement in the supply chain of thousands of pagers that detonated on Tuesday in Lebanon in a deadly blow to Hezbollah.

Explosions were reported in southern Lebanon, including the city of Sidon, as well as Beirut's southern suburbs and the Bekaa Valley At least 20 people have been killed and more than 450 wounded by a second wave of explosions from wireless communication devices in Lebanon,

Additional explosions linked to electronic devices caused more deaths and injuries a day after pagers used by Hezbollah exploded, wounding thousands.

The Hezbollah militant group said it is conducting a "security and scientific investigation” into the explosion of pagers across Lebanon on Tuesday.