U.S. stocks reversed early losses on Thursday with a report from the Wall Street Journal suggesting buyers have emerged for troubled regional bank First Republic (FRC).

Markets opened lower after the European Central Bank surprised with a 0.50% interest rate hike amid continued concerns over the global banking system but inflation that remains "too high" in the view of central bankers. Near 10:50 a.m. ET, the S&P 500 (^GSPC) was up 0.6%, the Dow Jones Industrial Average (^DJI) was higher by 0.2%, while the tech-heavy Nasdaq Composite (^IXIC) led gains, rising just less than 1%.

Futures had been mixed early Thursday ahead of the ECB's announcement. Wednesday's turmoil in Credit Suisse and a late-night intervention from the Swiss National Bank pushed investors to expect a more modest 0.25% increase from the ECB as central banks weigh financial stability concerns against inflation that remains elevated.

"Inflation is projected to remain too high for too long," the ECB said in its statement. "Therefore, the Governing Council today decided to increase the three key ECB interest rates by 50 basis points, in line with its determination to ensure the timely return of inflation to the 2% medium-term target."

"The Governing Council is monitoring current market tensions closely and stands ready to respond as necessary to preserve price stability and financial stability in the euro area," the statement added. "The euro area banking sector is resilient, with strong capital and liquidity positions."

Late Wednesday, Credit Suisse announced it would borrow up to 50 billion Swiss francs, or about $54 billion, from the SNB.

Shares of Credit Suisse (CS) fell as much as 30% on Wednesday after its largest investor, the Saudi National Bank, said it would not increase its stake in the trouble bank, citing regulatory challenges to taking its stake north of 10%.

Credit Suisse shares trading in New York were up about 5% in late morning trade Thursday.