TOCOM prices were not affected by the worst quake to hit Japan in 140 years, as the market had closed earlier.
The benchmark rubber contract on the Tokyo Commodity Exchange dropped 15.4 yen, or 3.7 percent, to settle at 401.4 yen ($4.84) per kg.
It fell as low as 392.3 yen, the lowest since Dec. 16, before rebounding slightly to finish above the major support level at 400 yen.
At its low, it had fallen by more than a quarter from the record high of 535.7 yen hit in mid-February. TOCOM rubber started early this week because of worries grew about the global economy; heavy stop-loss selling was seen.
The most active Shanghai rubber contract for May delivery fell 995 yuan to finish at 35,195 yuan ($5,353) per tonne.
Nikkei share futures in Singapore fell below 10,000 after an earthquake measuring 8.9 struck off the northeast coast of Japan. The benchmark Nikkei average in Tokyo ended the day at a five-week low, falling 1.7 percent to 10,254.43.
The quake hit northern Japan, causing a tsunami, power outages, fire and flight cancellations.
TOCOM prices were not affected as the market had closed before the quake hit Japan. However, it could have a negative impact on stock markets as well as TOCOM prices next week, dealers said.
Dealers said there were fears about possible damage to stocks in warehouses outside the capital city, which would prompt buying on the physical side.
Dealers said TOCOM rubber was still supported by limited supply on the fundamental side, which triggered speculative buying on the futures market below 400 yen, pushing prices above that support level.