The ship, which has been ablaze for almost a week since it collided with another vessel Saturday night in the East China Sea, was about 300 km (186 miles) northwest of Sokkozaki on the island of Amami Oshima as of Thursday afternoon, a spokesman from the Coast Guard's 10th region based in Kagoshima said.
Amami Oshima is one of the northern islands in the Ryukyu islands chain that includes Okinawa.
Highly flammable oil
The tanker Sanchi, owned by Iran's top oil shipping operator National Iranian Tanker Co., was carrying almost 1 million barrels of condensate, an ultra-light, highly flammable crude oil, to South Korea.
It collided with the freighter CF Crystal that was carrying grain from the United States about 160 nautical miles (184 km) off China's coast near Shanghai.
The spokesman said that Chinese authorities turned down an offer from the Japanese Coast Guard to help, saying it would ask for help when needed.
The Coast Guard has sent patrol boats and aircraft to monitor the situation, he said.
Drifts 25 miles in two days
According to China's state-owned China Central Television (CCTV), the tanker drifted about 25 miles (40 kms) to the south over the past two days, as of 9 a.m. (0100 GMT) on Friday.
About 14 rescue vessels are attempting to put out the fire and searching for missing crew members from the tanker, CCTV reported citing Shanghai Maritime Search and Rescue Centre.
The Sanchi had a crew of 32 sailors at the time of the collision. The body of a mariner suspected to be from the ship was recovered Monday and sent to Shanghai for identification.
The rest of the crew, which included 30 Iranians and two Bangladeshis, remains missing.