The collision, in the mouth of the Yangtze River Delta, occurred on Saturday evening.
The exact cause is not yet known.
What is the Sanchi carrying?
The tanker, run by Iran’s leading oil shipping operator, has on board 136,000 tonnes of condensate.
That is about one million barrels and at current prices is worth roughly $60m (£44m).
The Sanchi will also be carrying a certain amount of heavy – and toxic – shipping fuel.
Condensate is very different from the black crude that is often seen in oil spills.
It exists in gas form within high-pressure oil reservoirs and liquefies once extracted.
It is toxic, low in density and considerably more explosive than regular crude oil.
Condensate, which does not need the heavy refining process of denser crude, creates products such as jet fuel, petrol, diesel and heating fuel.
How does this compare with other oil spills?
It is impossible to say at this point because it is unknown how much oil has been, or will be, spilled.
The Sanchi’s one million barrels is about 35 million gallons. Even if all of it spilled, it would be less than the major ship disasters listed below, but more than three times the Exxon Valdez spill in 1989, which is considered one of the world’s worst environmental disasters.
So, how much the spill affects the environment depends on the location where it occurred. The Atlantic Empress incident listed below – the record spill from ships – saw little oil reach coastlines.
Image copyrightAFPImage captionCleaning up after the Torrey Canyon disaster in 1967
There are also a lot of different types of spill. Arguably the worst was the deliberate release of up to 500 million gallons by the Iraqis in January 1991 during the Gulf War. The resultant slick covered some 10,300 sq km (4,000 sq miles).
As far as ships are concerned:
The Atlantic Empress and Aegean Captain collided off Trinidad and Tobago in 1979. The Atlantic Empress exploded and 26 crew members died. The 90 million gallon oil spill is a record from ships
The ABT Summer exploded off Angola in 1991, spilling about 80 million gallons over 200 sq km
The Castillo de Bellver caught fire and broke apart off Cape Town, spilling 78 million gallons
The Amoco Cadiz spilled almost 69 million gallons after running aground off Brittany in France in 1978
The Torrey Canyon hit a reef off Cornwall, England, in 1967, spilling 36 million gallons of crude and affecting almost 200 miles of coastline
The Exxon Valdez only spilled 11 million gallons in Prince William Sound, Alaska, in 1989 but was a major environmental disaster