In the face of growing international concern, US Secretary of State Mike Pompeo scrapped a planned visit to Moscow and headed to Brussels instead for talks Monday with European officials.
The region is already on edge because of the standoff between Washington and Tehran over the Iran nuclear deal.
The US, which is is deploying aircraft carrier and bombers in the region to counter Iranian threats, has warned that "Iran or its proxies" could be targeting maritime traffic.
The accident occurred on a highway linking the capital Kinshasa to the country's sole seaport at Matadi on the Atlantic Ocean.
The collision, between a Panama-registered oil tanker and a Hong Kong-registered bulk freighter, took place on Saturday night in waters about 160 sea miles east of the Yangtze River's estuary.
In many of the most deadly of these cases, people were trying to recover spilt fuel and were caught in the subsequent fire.
The tanker flipped over Sunday and the fire from the oil spill engulfed scores of residents who had rushed to collect leaking fuel.
The police officials suspect that it could be an extortion threat to the oil transporters.