MOSCOW - Russian President Vladimir V. Putin gave Ukraine's hard-pressed government a strong financial assist in the form of a $15 billion loan and a sharp cut in the price of natural gas Tuesday, preempting European Union leaders.

With their protest encampment in Kiev, the capital, now in its fourth week, demonstrators demanded to know what terms President Viktor Yanukovych had agreed to during his one-day visit to the Kremlin to land such a deal.

Vitali Klitschko, the former boxer who heads the opposition UDAR party, said in an address to protesters Tuesday evening that he believed Yanukovych secured the loan with Ukrainian property - perhaps the natural gas pipeline network - as collateral.

"Only early elections can be a solution for the country," Klitschko said. "Yanukovych told us at the roundtable [Friday] that he is not afraid of early elections. I am challenging Yanukovych. ... I am calling him to the ring."

The risk to Putin is twofold: He has potentially embroiled Russia in both Ukraine's weak economy and its political passions.

The two countries also signed a package of lesser trade accords, amid agreement that they need to reduce trade barriers. Afterward, Yanukovych said, "I will say openly: I know that this work wouldn't have been done at this optimal speed if not for the Russian president's political will."

The conditions of the loan were not disclosed. Putin said the drop of about 33 percent in the price of gas might be temporary.

Ukraine, heading for financial straits, has been bobbing and weaving between the European Union and Russia. Tuesday's deal lifts some of the immediate financial pressure but does not appear to be a clear signpost for Ukraine's future.

The key question will be whether Ukraine keeps talking to the EU about new terms for a trade pact or whether its recently renewed negotiations with the bloc were merely a ploy to get Putin's attention.

A desire to side with Europe is what drew protesters out in late November, and Tuesday's development could see the domestic pressure on Yanukovych mount.