Stocks stabilize after turbulence last week

The S&P 500 gained 19.18, or 1.5 percent, to 1,298.38, gaining 3.3 percent since March 16, its best three-day advance since the first week of December.

AT&T was up 1.2 percent, while Verizon increased 1.7 percent, following the announcement of the agreement for AT&T to buy T-Mobile. 

The Nasdaq composite rose 48.42, or 1.8 percent, to 2,692.09. 

U.S. markets have fluctuated wildly in the aftermath of the Japanese earthquake, uprisings in the Middle East and North Africa and rising oil prices. 

Those concerns ebbed over the weekend after the Nuclear Regulatory Commission said the situation at the Fukushima nuclear plant appeared to be stabilizing.