WASHINGTON — Shares of Fannie Mae and Freddie Mac soared yesterday in a respite from their battering in recent days, while some regional banks saw their stocks sink on worries they could be swept up in the turmoil surrounding the mortgage-finance giants.

Freddie completed a $2-billion debt sale, and a Wall Street analyst said a government bailout of the mortgage finance giants may not be inevitable.

But a few regional banks with significant holdings in preferred stocks of Fannie and Freddie followed the rest of the market down amid questions over whether federal regulators would step in to rescue the two government-sponsored companies.

Shares of Freddie jumped 48 cents, or 17.1 percent, to $3.29 yesterday, while Fannie climbed 19 cents, or 3.8 percent, to $5.19.

Citigroup analyst Bradley Ball said in a research note that federal bailouts “don’t necessarily wipe out all” company shareholders, and that Fannie and Freddie still have options despite their steep stock declines in recent weeks.

“We are not convinced that [the government] needs to take any action over the near term,” Ball wrote.

But Len Blum, managing director and partner at investment bank Westwood Capital in New York, said the rebound is likely to be temporary, as the companies’ ability to raise capital on their own appears uncertain.

“The market thinks they’re going to be nationalized,” Blum said. “People have confidence in the debt, not the equity.”

Freddie’s sale of $2 billion in short-term debt was well received on Wall Street, but the company had to sweeten terms of the offer to lure demand, investors said. “We saw very good demand for today’s deals,” said Freddie Mac spokesman Michael Cosgrove.

In the coming weeks, Wall Street will be watching the results of several such auctions by the two companies. Sean Egan, manager of the ratings desk at Egan-Jones Rating Co., estimates the two companies have a combined $295 billion in debt coming due by year-end.

“It’s becoming increasingly expensive for both Fannie and Freddie to fund their business,” he said. “If that’s not addressed fairly soon, the companies will continue to be under stress.”

A government rescue of Fannie and Freddie — whose share prices have plunged in recent weeks as they struggle with billions of dollars in losses from bad mortgages — could be costly for scores of investment, banking and insurance companies that hold billions in their preferred shares.

The two companies had nearly $36 billion in preferred shares outstanding as of June 30, according to filings with the Securities and Exchange Commission.

Preferred shares usually pay a fixed dividend and have priority over common stock when it comes to dividends and bankruptcy liquidation. While slightly riskier than bonds, which have the highest priority in times of trouble, companies often invest in preferred shares for certain tax advantages.

JPMorgan Chase & Co. disclosed yesterday that it held about $1.2 billion of Fannie and Freddie preferred shares. It estimated the shares have lost about $600 million since the start of the quarter on July 1, based on their current market values.

Shares of JPMorgan fell $1.54, or 4.1 percent, to $36.13 yesterday, while the major Wall Street indexes lost about 2 percent.