The Iranian tanker, Sanchi, has been ablaze since it collided with Hong-Kong registered freight ship CF Crystal on Saturday night, 185 miles off China's coast near Shanghai.
Efforts to extinguish a fire and rescue survivors on a stricken oil tanker have been hampered because the vessel keeps exploding.
The spokesman of Japan's Coast Guard stated that China has rejected Japan's offer for providing assistance in extinguishing the fire and rescuing the sailors and has said that in case the need arises, they will call for help from Japan.
There have been continuous explosions onboard the ship, China's official Xinhua news agency said late on Friday, citing the Ministry of Transport.
The Sanchi was carrying almost 1 million barrels of condensate, a type of gassy, ultra-light oil, when it collided Saturday evening with a freighter 257 kilometers (160 miles) off the Chinese coast and caught fire.
Of the 30 Iranians and two Bangladeshis on the Sanchi's crew, only one body has so far been found.
Sanchi was carrying nearly one million barrels of highly flammable crude oil to South Korea with 32 crew members on board - 30 Iranians and two Bangladeshis. The Chinese freighter CF Crystal. had 21 crew members, who all were reported safe.
The Coast Guard has sent patrol boats and aircraft to monitor the situation, said a spokesman for the Japan Coast Guard's 10th region based in Kagoshima.