BERLIN (AP) _ Riot police swinging truncheons charged into crowds of rock-hurling leftist militants protesting the World Bank-International Monetary Fund talks. Paramedics said both police and protesters were injured.

The street battle took place Monday night after about 1,500 people staged a demonstration downtown to protest what they called unfair financial policies of industrialized nations toward heavily indebted Third World countries.

Finance ministers of 22 countries are attending the annual meeting along with thousands of other finance officials. The talks open officially today with a speech by West German Chancellor Helmut Kohl.

Violence erupted Monday night after police had broken up the demonstration. About 500 radicals blockaded streets leading to the German Opera, where hundreds were watching a production of Mozart's ''The Magic Flute'' staged especially for delegates and guests of the financial discussions.

Some protesters left after warnings by police but others refused to go, witnesses said.

A large contingent of helmeted police then moved in, swinging their truncheons as demonstrators hurled rocks, the witnesses said.

About 100 demonstrators ran to a square near West Berlin's famed Kaiser Wilhelm Memorial Church where the violence continued.

Some protesters were seen being hauled into police vans during the two-hour battle. A police spokesman said he did not know how many people had been arrested or injured.

About 2,700 police from across West Germany have been sent to West Berlin to help the city's 6,000-strong police force during the week of financial talks.

In talks today, the head of the International Monetary Fund urged industrial nations to keep their economies expanding - but with low inflation - to help ease the hardships suffered by the heavily indebted poor countries.

Michel Camdessus told the annual meeting that the rich countries must be on guard against a fresh surge in prices.

''The central requirement is to avoid the return of inflationary psychology,'' he said in a prepared text of his speech.

Camdessus noted ''a few scattered warning signals,'' including tightening labor markets in some countries and higher prices for some commodities.

U.S. Treasury Secretary Nicholas Brady, attending the first international policy talks in his new job, also was scheduled to speak today. Japan's central bank governor, Satoshi Sumita, was expected to offer details of his country's proposal to help big debtor countries like Brazil and Mexico.

In his speech, Camdessus appealed to the United States to reduce its government spending.

''''Fiscal restraint,'' he said, ''is currently warranted in several countries, most notably the United States ...''

''A stronger budgetary position in the United States would also help make exchange markets more resilient in the face of unexpected developments,'' he said. ''And it would lower real interest rates, with beneficial effects for indebted countries.''

Camdessus applauded the industrial nations' decision to lighten the money problems of the poorest debtor countries, mostly in sub-Saharan Africa, and called on bankers and governments to do more for the large debtors.

World Bank President Barber Conable made an impassioned appeal to wealthy countries to fight world poverty.

''Poverty on today's scale prevents a billion people from having even minimally acceptable standards of living,'' he said in the prepared text of his remarks.

''To allow every fifth human being on our planet to suffer such an existence is a moral outrage,'' he said.

The meeting is scheduled to last through Thursday.