ATHENS—A wave of protests against home repossessions has swept Greece in recent weeks, prompting fears for the safety of workers carrying out the forced transfers and threatening plans to clean up the country’s banking system.

The rise in sometimes-violent activism by leftist groups comes as banks in Europe’s most depressed economy push to resume seizures and auctions of properties, especially commercial real estate, to pare their books of bad loans. The sector is sitting on some €108 billion ($118.6 billion), or 45% of its total loans, a figure that covers all categories from mortgages to consumer and business loans.

Similarly, the Greek state has pledged to auction off properties of people who owe it large amounts of unpaid taxes or social-security contributions.

But attempts to kick-start the auction process this June haven’t gotten far. A string of auctions since then have been canceled due to protests. After violent clashes on Oct. 5, when protesters fought with police at a courthouse in Thessaloniki, notaries refused to carry out further auctions. On Wednesday, notaries resumed auctions in several cities and again faced demonstrations, including in Thessaloniki, where protesters barged into court and prevented an auction.

Left-wing political movements have been leading the protests, including the activist group Den Plirono, meaning “I Won’t Pay” in Greek. “The growth of the movement against auctions is causing panic for the government, bankers and other vultures,” the group said in a statement.