Ship traffic in Turkey's Bosphorus Strait was briefly suspended on Wednesday morning after a vessel suffered an engine failure, the Tribeca shipping agency said.
The Liberian-flagged crude oil tanker Guanyin encountered the problem at the strait's northern entrance.
Shipping was set to resume through the strait shortly after two tugs were sent to provide assistance, Tribeca said.
Millions of barrels of oil pass through the 19km-wide strait each day, a crucial passageway for global trade.
Connecting the Black Sea to the Mediterranean, the Bosphorus was also vital to the UN-brokered grain deal, which collapsed in July.
The tanker was carrying diesel fuel and vacuum gasoil, Reuters reported.
In January, a Ukrainian cargo ship ran aground in the strait, several months after another carrying about 2,720 tonnes of Ukrainian grain also ran aground.
Traffic was also briefly suspended after a vessel suffered engine failure on the strait in February.
While incidents are usually resolved relatively quickly, a tanker logjam in December halted traffic along the strait for several days, holding up dozens of ships waiting to pass through.
The logjam raised the risk of a geopolitical crisis as Turkey demanded proof of insurance from vessels passing through the strait and docking at Turkish ports, analysts said.
It came only days before a western-imposed $60 price cap on Russian oil, which also barred insurers from covering tankers transporting oil priced above the agreed cap.