UPDATE 3-Putin's oil tsar slams OPEC and U.S., launches broadside at price crash
* Igor Sechin says "OPEC has lost its teeth"
* Criticises U.S. export ban as protectionist
* IEA says Russian will be amongst hardest hit by oil crash (Recasts, adds quotes, background)
By David Sheppard and Ron Bousso
LONDON, Feb 10 (Reuters) - The head of Kremlin-controlled energy giant Rosneft targeted OPEC and the United States on Tuesday as he launched a broadside at the forces behind the oil price crash that has hit Russia's economy hard.
Igor Sechin, one of President Vladimir Putin's closest allies, said during a rare visit to London that OPEC had erred in not cutting output, as he blamed the low oil price on factors from financial speculators to U.S government policy.
Oil has more than halved since June as fast-growing U.S. shale supplies overwhelmed demand. The decline accelerated after the Organization of the Petroleum Exporting Countries, of which Russia is not a member, chose to try protect its market share rather than cutting output to support prices.
"OPEC has lost its teeth," Sechin said through an official translator at London's International Petroleum Week, an annual industry event. OPEC's decision to let prices fall had led to a "destabilisation" of the market, he said.
Sechin, who has been targeted by Western sanctions over Russia's role in the Ukraine crisis, said the sharp collapse in oil could not be explained only by the forces of supply and demand, hinting there may be other factors at play. Continuación...