Four Korean tourists and one Yemeni man were killed when a bomb exploded at a tourist site in southern Yemen late Sunday.

The South Korean Embassy in Yemen said the blast occurred around 5:50 p.m. on Sunday local time, hitting a group of 18 Korean tourists who were sightseeing in Shibam, an ancient city that is recognized by UNESCO as a World Heritage site.

The identities of the four killed in the explosion have been confirmed. Three more tourists suffered injuries.

The Korean tourists entered Yemen last Tuesday and were scheduled to fly home on Monday.

The Associated Press said the explosion was likely a suicide bombing. A Yemeni security official says the blast occurred while the tourists were driving near Shibam.

Last year, two Belgian tourists were shot and killed in Yemen by armed militants suspected of having connections to Al-Qaeda.