A Romanian ship collided with a Bulgarian tugboat and sank in the Danube River on Sunday, and 151 people were missing, Romania's official Agerpres news agency reported.
A British newspaper said many of the passengers aboard were Western tourists.
The collision occurred upstream of the port city of Galati, about 125 miles northeast of the Romanian capital of Bucharest, the report said, adding that the ship sank "in conditions of poor visibility."
A total of 169 passengers were aboard the Romanian ship. Only 18 of them and the ship's 13 crew members had been rescued, Agerpres said. It did not give the nationality of the passengers.
The Bulgarian state news agency BTA said the Romanian cruise ship Mogosoaia collided with the Bulgarian ship Peter Karaminchev, which was towing loaded barges.
"After the alarm was sounded by the Bulgarian ship, its crew and the crew of the ships in the proximity ran to help," BTA said. There were no reports of casualties aboard the tug, the agency added.
There was no report on what caused the boats to collide.
In London, an early edition of the Independent newspaper said that apart from the 13 crew members, most of the 169 passengers aboard the Mogosoaia "were almost certainly Western tourists." The newspaper report from Vienna quoted Danube shipping officials in the Austrian capital.
Pleasure cruises on the Danube are one of Romania's few sources of hard currency, the paper said.
Agerpres said that rescue operations were continuing and that a government commission was established to investigate.
The Independent blamed Agerpres for "sparse details" of the sinking, which only began to emerge 10 hours afterward. It said the Bulgarian BTA news agency "was no more informative."