ROME — The price of Fiat shares is soaring after the Italian automaker announced it had clinched a deal to acquire the rest of Chrysler, with no plans for a capital increase.

The share price on the Milan exchange soared 12 percent today, having been up by as much as 15.8 percent earlier in the day.

Fiat SpA trumpeted the announcement Wednesday night that it had reached an agreement with the United Auto Workers union-controlled trust fund holding 41.5 percent of Chrysler’s shares. Fiat already possesses the remaining shares. Fiat says it will pay $1.75 billion in cash at hand.