Japan earthquake death toll rises to 28 as evacuees battle sweltering heat
Thousands of personnel have been deployed for search-and-rescue operations. Many are digging through rubble at Kashima's Aeon shopping centre, one of the worst-hit buildings where a section of the second floor collapsed.
The promenade was also rocked by an explosion about an hour after the initial quake.
The president of Aeon said it was "very likely" a state explosion, though the origin of the blast remains under investigation.
A cat cafe in the promenade said on Wednesday that its 25 cats, which had been left behind during the chaos of the quake, had each since been safely rescued.
The quake-hit Aeon promenade in Kumamoto had just reopened last month as a revamped shopping complex. It had previously been damaged during a series of strong earthquakes in April 2016, which killed 278 people in the region.
Rescuers were also combing a Nippon Paper mill in Yatsushiro city, where at least 5 people died after the mill partially collapsed during the quake.
Eleven people were trapped in the building, seven of whom have been rescued so far, Nippon Paper said in a statement on Wednesday.
The quake, which had a shallow depth of 10km (six miles), shocked residents across Kumamoto.
Hiroko Ogata, a 75-year-old building proprietor in the city of Yatsushiro, told the BBC she "hid nether a array astatine her edifice erstwhile the quake struck and swayed violently on with it".
She added, "I person lived present for 75 years, but I person ne'er experienced specified a large quake," she said. "I thought I would die."