AFP - Brazil's president pledged to spend 60 million dollars on security and prove the country could successfully host the 2014 World Cup and the 2016 Olympics after drugs gangs shot down a helicopter.

More than 1,700 officers were deployed in northern Rio de Janeiro, scene of weekend clashes between drug gangs and police that authorities said left 22 dead.

Three of those killed were policemen in a helicopter brought down on Saturday as it surveyed a turf war between rival gangs in the Morro dos Macacos slum.

The incident triggered a massive ground confrontation between police and gangs on Saturday and Sunday that left at least 14 residents dead. Police said most were suspected gang members, though at least three appeared to be civilians caught in the crossfire.

A spokesman, Major Oderlei Santos, told Globo television the anti-gang operation was open-ended and "the military police will work tirelessly to track down and capture these criminals."

President Luiz Inacio Lula da Silva, speaking on a visit to Sao Paulo, on Monday condemned the weekend violence and said he offered Rio state governor Sergio Cabral "any help he needs, including the National Guard."

The Wall Street Journal reported Tuesday that Lula promised to allocated 60 million dollars in aid to Rio, amid fears over whether the city would be ready to host the 2014 World Cup and 2016 Olympics.

Lula has said his government is tackling the endemic violence in the city's slums and "clean the dirt" marring Rio's image.

Around a third of Rio's population of six million live in the 1,000 slums nestled in the coastal city. Known as favelas, the shanty-towns in some cases abut the popular tourist beach areas of Ipanema and Copacabana.

Violence is rife, with 6,000 homicides recorded last year. Muggings are extremely common.

Frequent clashes between police and slum gangs intensified since mid-2007, when Governor Cabral declared war on the heavily-armed criminals.

The head of Rio's security secretariat, Jose Mariano Beltrame, said it was believed a big ".38- or .50-caliber" automatic gun brought down the police helicopter on Saturday.

"The firepower of Rio's drug dealers is frightening," Dilson Ferreira Anaide, head of Rio state's military officers' association, told AFP.

"The bandits now have weapons capable of shooting down small planes; that's really serious. This is the first time, in Rio and in Brazil, that they've brought down a helicopter," he said.

Prison has also proved no deterrent to organized criminals. Many are controlled, at least in part, by gangs that ensure lines of communication between incarcerated chiefs and their underlings.

The turf war that started the weekend violence in Rio was believed to have been ignited by a drug kingpin being held in a maximum-security facility in southern Brazil who tried to take over a rival gang's territory, according to police sources cited in media reports.

The country's parlous security situation has long been known, but increasing international scrutiny ahead of the World Cup and Olympics is making authorities uncomfortable.

The weekend violence in Rio "is terrible for the image of a city that is to welcome the World Cup in 2014 and the Olympics in 2016," Ferreira Anaide acknowledged.