The Turkish president, Recep Tayyip Erdogan, is stepping up his operation to purge his opponents, with the latest victim being Constantinople Mayor Ekrem Imamoglu, who has been arrested and detained by authorities. This development was immediately reflected in Turkish assets and the stock market, as the Turkish lira plunged, while the sell off of stocks caused a halt in trading.

Meanwhile, government bond yields soared to their highest levels this year as investors fled the country’s assets after the arrest as political risk increased.

The benchmark Borsa Istanbul 100 index fell 6.9 percent at the open, triggering a trading suspension under the exchange’s circuit-breaking rules. Shares were 4.6 percent lower at the reopening.

Treasury 10-year bonds fell, sending yields 175 basis points higher to 29.94%. The pound fell more than 5% against the US dollar. The declines were the worst in the world among comparable asset classes.

Ekrem Imamoglu, was detained Wednesday morning, a day after Turkish authorities revoked his university diploma, in a move that could prevent him from challenging Erdogan in the next presidential election. Among Turkey’s most popular politicians, the 54-year-old is considered a leading candidate for the presidency. He defeated Erdogan’s chosen candidate in last year’s race for Istanbul mayor and on Sunday was set to be named presidential candidate of the Republican People’s Party, the main opposition group known as the CHP.

“Turkish assets are under strong selling pressure,” said Piotr Matys, a senior currency analyst at In Touch Capital Markets. “For some investors, it is also a reminder that President Erdogan intends to cling to power even more by trying to prevent his biggest political rival from running in presidential elections due in 2028, although early polls are not ruled out.”