The health ministry has dispatched a cluster response team to a southwestern Japan city due to a sudden rise in novel coronavirus cases, after a state of emergency was lifted in mid-May, the top government spokesman said Thursday.

City officials and residents in Kitakyushu have been on heightened alert for another wave of infections as transmission routes in many of the recently reported cases are untraceable, which could trigger an explosive surge in cases if unaddressed.

"The health ministry sent a team in charge of cluster response yesterday," Chief Cabinet Secretary Yoshihide Suga said at a news conference. "We will work with the local government to prevent the spread of the virus."