ATHENS — Authorities in Greece warned Tuesday that bars and restaurants could be shut down if they defy COVID-19 distancing rules following a jump in infections among young people.

Civil Protection chief Nikos Hardalias said one-week license suspensions will be imposed on businesses that serve standing customers or ignore capacity limits, followed by two-week and indefinite suspensions if the violations persisted. Fines will range from 2,000 to 10,000 euros ($2,360-11,800) depending on the size of the business and the number of previous infringements, he said.

The measures, which start Thursday, will also impact tourist resorts on the Greek islands and elsewhere where there have been frequent reports of overcrowding.

Greece is anxious to restart its vital tourism industry, which accounts for about a fifth of annual economic output, while at the same time avoiding a major surge in new infections.

Hardalias said there had been a "rapid surge in infections" among young people, noting that nearly a third of new cases are believed to have originated from crowded outdoor gatherings.

Greece ended the mandatory outdoor use of face masks on June 24, but the mandate remains in effect for all indoor public spaces.

A six-week decline in coronavirus infections ended in late June and the number has since risen from 3.4 daily cases per 100,000 people as a seven-day rolling average to 7.6.

"Since June 28 there has been a sharp and very fast rise in infections," Hardalias said, adding that the average age of people now testing positive has fallen to 27.

Hardalias said the rise in infections and increasing pressure from the highly contagious delta variant had added urgency to the vaccination campaign.

"We realize that our young people want to let off steam. They want to have fun," he said. "So we are again appealing to them, with friendly encouragement, to get vaccinated immediately, regardless of their strong desire to seek entertainment."