Japan’s prime minister, Fumio Kishida, has cancelled a visit to central Asia this weekend after experts warned that the risk of a “megaquake” occurring off the country’s Pacific coast had increased following Thursday’s magnitude 7.1 earthquake in the south-west.

Kishida, who is battling low approval ratings and faces challenges to his leadership in a ruling party presidential election next month, announced his decision at a press conference on Friday.

He had been due to hold a summit with the leaders of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan in the Kazakh capital Astana on Friday evening and to meet the Mongolian president in Ulaanbaatar on Monday, according to the Kyodo news agency.

The Japan Meteorological Agency on Thursday issued its first-ever warning of the risk of a huge earthquake along the Pacific coast after a quake on the southernmost main island of Kyushu triggered a tsunami warning. No deaths or major damage have been reported.