Samsung said it is halting sales of the Galaxy Note 7 smartphone after a spate of fires involving new devices that were supposed to be safe replacements for recalled models.
The firm said consumers with original Note 7 devices or replacements they obtained after the recall should turn off the power and seek a refund or exchange them for different phones.
Meanwhile, South Korean authorities said in a statement they had found a new product defect in the Note 7 and asked consumers to power them down or to exchange them. The statement did not identify the defect.
Officials from the US Consumer Product Safety Commission echoed the advice in their own statement, adding that they are continuing to investigate at least five incidents of fire or overheating reported since a formal recall was announced on September 15.
"No-one should have to be concerned their phone will endanger them, their family or their property," said Elliot Kaye, chairman of the safety commission. He called Samsung's decision to suspend all sales "the right move" in light of "ongoing safety concerns".
The announcement follows several new incidents of overheating last week and deals a further blow to the world's largest smartphone company. Leading networks have already said they will stop distributing new Note 7 phones as replacements for the earlier recall.
Analysts said the new problems pose a crisis for the South Korean tech giant, which is locked in fierce competition with Apple and other leading smartphone makers.
"This has been a real black eye on the product," said Ben Bajarin, a consumer tech industry analyst with the Creative Strategies firm.
The new reports also raise questions about the cause of the problem. Samsung has blamed batteries provided by a particular supplier, while assuring consumers that the phone was otherwise safe. It said it solved the problem by switching to batteries from another supplier.
The tech conglomerate reported last week that its overall profits increased in the last quarter, thanks to booming sales in other corporate units that sell computer chips and display screens.
Samsung sells far more units of its Galaxy S7 phones than the more expensive Note 7, but analysts worry the issue could hurt the company's reputation and overall standing with consumers.
Samsung sells about a third of all high-end smartphones, while Apple sells slightly more than half, according to Credit Suisse investment analyst Kulbinder Garcha.
He predicted that the new Note 7 problems will help Apple increase its share of the market.