The S&P 500 and Nasdaq Composite tumbled intraday as concerns regarding artificial intelligence competition from China's DeepSeek rattled the US technology sector.

The tech-heavy Nasdaq slumped 3.3% to 19,292.2 after midday Monday, while the S&P 500 declined 1.8% to 5,989.5. The Dow Jones Industrial Average rose 0.3% to 44,550.4. The tech sector sank 6%, while utilities dropped 3.1%. Consumer staples paced the gainers.

DeepSeek recently launched a large language model that Wedbush Securities said "rivals" Meta's (META) Llama 3.1 and Microsoft (MSFT)-backed OpenAI's ChatGPT.

Chip-making giant Nvidia's (NVDA) shares tumbled 17% intraday Monday, the worst performer on the Dow and among the worst on the Nasdaq. Microsoft shares fell 3%, while Meta was up 0.3%. Broadcom (AVGO) slid 19%, the steepest decline on the Nasdaq and among the steepest on the S&P 500. Marvell Technology (MRVL) and Micron Technology (MU) were also among the worst Nasdaq performers.

DeepSeek's AI assistant overtook ChatGPT as the top-rated free app on Apple's (AAPL) US App Store over the weekend, news outlets reported. The iPhone maker's shares were up 3.9% intraday Monday, the best performer on the Nasdaq and the second-best on the Dow.

AT&T (T) logged better-than-expected fourth-quarter results and reiterated its full-year earnings outlook. The telecommunications giant's shares jumped 7.2%, the top gainer on the S&P 500.

The US 10-year yield fell 8.9 basis points to 4.53% intraday, while the two-year rate lost 7.7 basis points to 4.2%.

In economic news, new-home sales in the US rose in December, while median prices at the national level picked up both sequentially and annually, government data showed.

"Looking past January, we expect new home sales to improve modestly in 2025, based on our forecast for mortgage rates to decline modestly over the course of the year," Oxford Economics said.

West Texas Intermediate crude oil was down 2.4% at $72.84 a barrel intraday.

Gold dropped 1.4% to $2,739.30 per troy ounce, while silver fell 2.2% to $30.50 per ounce.