May 15 marks the 50th anniversary of Okinawa's return to Japan from US rule following the end of World War Two.

About 80 percent of respondents in an NHK survey say they think it's wrong for the majority of US military facilities in Japan to be concentrated in the southwestern prefecture of Okinawa.

The survey, which was carried out in February and March, polled 1,800 people in Okinawa and 1,800 people across the rest of Japan. Over 800 people in Okinawa and over 1,100 people from other areas of the country responded to the survey.

Around 70 percent of US military facilities in Japan are in Okinawa. Fifty-six percent of respondents in Okinawa and 24 percent in other parts of Japan said they disapproved of this.

Twenty-eight percent of respondents in Okinawa and 55 percent in other parts of Japan said they rather disapprove.

Eight percent of respondents in Okinawa and 13 percent in other parts of Japan said they tended not to disapprove.

Five percent of respondents in Okinawa and 7 percent in other parts of Japan said they did not disapprove.

In Okinawa, more than 80 percent of respondents disapprove or rather disapprove of having US military facilities concentrated in their prefecture.

Meanwhile, 11 percent of respondents in Okinawa and 12 percent in other parts of Japan said they thought the US bases were necessary for Japan's security, while 51 percent in Okinawa and 68 percent in other parts of Japan said they thought it was unavoidable for Japan's security.

But 19 percent of respondents in Okinawa and 14 percent in other parts of Japan said the bases are not necessary for Japan's security. Another 17 percent in Okinawa and 5 percent in other parts of Japan said the bases could pose a threat to Japan's security.