U.S. stock index futures slid on Tuesday, with banks stocks declining further as the Russia-Ukraine crisis deepened, while a rise in oil prices supported shares of energy companies.

Citigroup slipped 1.6% in premarket trading to lead losses among the big banks as the U.S. 10-year Treasury yield dropped to 1.7565, its lowest level since Jan 3.

European stock markets sagged, oil jumped back above $100 a barrel as a Russian armored column bore down on Ukraine's capital Kyiv on Tuesday. Russia's defense minister said Moscow will continue its military operation in Ukraine until it achieves its goals.

Oil majors Exxon Mobil and Chevron Corp rose about 0.6% each as oil prices surged. Chevron also raised its share buyback program and forecast for operating cash-flow through 2026.

Defense stocks, including Lockheed Martin Corp, edged higher, building on a sharp rally in the previous session. Shares of Tesla Inc dipped 1.3%, making them the biggest decliner among the mega-cap growth names.

At 06:09 a.m. ET, Dow e-minis were down 188 points, or 0.56%, S&P 500 e-minis were down 26.75 points, or 0.62%, and Nasdaq 100 e-minis were down 93 points, or 0.65%.

All the major indexes logged their second straight month of losses on Monday, with the S&P 500 index down over 8% so far in 2022, its deepest two-month decline since March 2020.

The CBOE volatility index, also known as Wall Street's fear gauge, was last trading at 31.40 after hitting its highest level since Feb. 24 in the previous session.