Stocks traded mostly lower by the end of Monday's volatile trading session as investors eyed talks between Russian and Ukrainian officials alongside another batch of santicions raised by the U.S. and its allies against Russia. The Dow Jones Industrial Average fell by nearly 200 points and the S&P 500 Index dropped nearly 0.2%. Meanwhile, the Nasdaq Composite rose over 0.4% as market participants bought the dip in tech names.

Here's how the market settled to start the week:

S&P 500 Index (SPY  ): -0.24% or -10.71 points to 4,373.94

Dow Jones Industrial Average (DIA  ): -0.49% or -166.15 points to 33,892.60

Nasdaq Composite Index (QQQ  ): +0.41% or +56.78 points to 13,751.40

Shell to end partnership with Russian-owned Gazprom:

Shell (SHEL  ) announced Monday it is ending its "equity partnership" with Russian state-owned energy company Gazprom (OGZPY  ) due to the ongoing Russia-Ukraine conflict.

Shell said it's selling a 27.5% stake in Sakhalin-II, an integrated oil and gas project located on the Sakhalin island in Russia, alongside a 50% interest in Salym Petroleum Development N.V, while is "a joint venture with Gazprom Neft that is developing the Salym fields in the Khanty-Mansiysk Autonomous District of western Siberia." The company also said it's ending its involvement in the Nord Stream 2 pipeline project.

Shell's announcement comes a day after rival BP (BP  ) said it was unloading its 19.75% stake in Rosneft (OJSCY  ), another Russian-controlled oil company.

U.S. imposes more sanctions against Russia:

The White House announced additional sanctions against Russia's central bank early on Monday, now prohibiting Americans from doing any business with the bank as well as freezing its assets within the United States. The new sanctions, which took effect immediately, also taget the National Wealth Fund of Russian Federation and the Ministry of Finance of the Russian Federation.

"We wanted to put these actions in place before our markets open because what we learned over the course of the weekend from our allies and partners was the Russian Central Bank was attempting to move assets and there would be a great deal of asset flight starting on Monday morning from insitriautons around the world," a senior White House official told reporters, quoted by CNBC.

Here's how market benchmarks started trading soon after open:

S&P 500 Index: -1.10% or -48.34 points to 4,336.31

Dow Jones Industrial Average: -1.38% or -471.26 points to 33,587.49

Nasdaq Composite Index: -0.67% or -89.64 points to 13,603.10