"It was a big surprise to us, but probably to every Turkey-watcher", said Nora Neuteboom, an economist at ABN Amro, saying the move was a "positive signal" with the bank wanting to show its independence and commitment to fight inflation.
It described the hike as a "strong monetary tightening to support price stability".
TRT World's Turkey analyst Yusuf Erim has more.
But Neuteboom of ABN Amro said much more was needed for Turkey to turn around "the negative spiral" the economy is in.
"It nearly seems like it's a game of "good cop, bad cop" being played out between the Turkish authorities - with President Erdogan on the one hand still making statements regarding his dislike of interest rates and. a very sizeable reaction from the central bank in response to the recent inflationary and geopolitical developments".
There had been indications from Turkey's central bank that it would raise rates, after inflation came in at almost 18% in August, according to official data. "If you say 'inflation is cause, the rate is the result, ' you do not know this business, friend".
Ignoring calls for restraint from President Recep Tayyip Erdoğan, the bank raised its main short-term rate from 17.5% following weeks of pressure from worldwide investors.
Anthony Skinner, director of Middle East and North Africa at Verisk Maplecroft, told AFP he believed the hike had already been agreed.
The bank later said funding would be provided via the policy rate, the one week repo auction rate, instead of through overnight lending from September 14.
However, a diplomatic row with the United States and concerns about the president's influence on monetary policy have eroded investor confidence in Turkey in recent months.
TRT World journalist Mobin Nasir has the latest on the Turkish central bank's decision to increase interest rates to 24 percent.
The US earlier hit Turkey with tariffs on items such as steel and aluminium in an effort to increase pressure on the country to free the detained American pastor Andrew Brunson.