The search for dozens of earthquake survivors trapped under rubble has been described as a "race against the clock".
The threat of heavy storms and ongoing aftershocks have lent greater urgency to rescue efforts, with the country's authorities racing to help victims of two powerful earthquakes that struck south-western Japan.
Japanese prime minister Shinzo Abe said: "We're racing against the clock. We will provide more personnel if necessary." He revealed the US military extended an offer of help, but that it was not urgently needed yet.
At least 41 people have been killed and at least 1,500 injured as a result of the earthquakes, which were measured at 6.2 and 7.3 magnitude, according to Japan's Meteorological Agency.
Gen Aoki, head of earthquake and tsunami observation at the Japan Meteorological Agency, said in a statement: “As of now, lively earthquake activity is continuing from Kumamoto to Oita prefectures. There is an ongoing possibility of ground slips from more strong tremors or the rain since yesterday.”
Japanese police said they received 97 reports of people trapped or buried under collapsed buildings, while 10 people were caught in landslides.
Japan has deployed 25,000 self-defence forces for the rescue effort, according to chief cabinet secretary, Yoshihide Suga.
Mr Suga told a press conference workers are aware of multiple locations where victims “have been buried alive.”
He said about 70,000 people have sought shelter in emergency centres, adding: “Police, firefighters and Self-Defense Force personnel are doing all they can to rescue them.”
Many victims are feared trapped in collapsed homes and buildings, particularly in towns and villages cut off by collapsed bridges or landslides blocking roads and motorways.
The national government dispatched 20,000 troops – many trained especially for disaster relief operations – to join thousands of local police, firefighters and rescue workers.
There are now also growing concerns for the 250,000 that have been made homeless as a result of the earthquakes.
In response to the predicted bad weather, the government rushed additional rescue workers to the area, providing thousands of waterproof tarps to protect victims and workers.
Authorities fear heavy rain could trigger additional landslides in the mountainous region.
