MOSCOW (AP) - British Prime Minister David Cameron arrived in Russia for a rare visit Sunday, seeking to secure crucial new trade and warmer ties with an often difficult ally, five years after the poisoning death of a Kremlin critic in London exposed bitter differences.
Cameron was making the first visit to Russia's capital by a British leader in six years, and will hold the first talks by any British official with Prime Minister Vladimir Putin in more than four years - hoping to revive relations before the ex-president's possible return to power in a 2012 election.
Accompanied by Foreign Secretary William Hague and business executives, including oil company BP's chief executive Bob Dudley and Royal Dutch Shell CEO Peter Voser, Cameron will attempt on the two-day visit to increase trade with another awkward partner after similar trips to India and China.
Cameron wants to kick-start Britain's stagnant economy by targeting emerging markets, but the policy has caused concern among those who fear it may lead the U.K. to overlook the human rights records of new allies.
Ahead of the visit, Russia's Embassy in London said its website was brought down in an apparent cyberattack.
Ties between Britain and Russia soured over the 2006 poisoning death of dissident ex-Russian security agent Alexander Litvinenko in London. On his deathbed, Litvinenko accused Putin of authorizing his killing.
Russia has repeatedly refused British requests for the extradition of the chief suspect in the case, ex-KGB agent Andrei Lugovoi.
British government officials acknowledged Cameron would raise the issue, but said the leader's visit would be focused on businesses opportunities - knowing there is little prospect of progress on the Litvinenko case.
Litvinenko's friend Alex Goldfarb said the dissident's widow and associates were disappointed that Cameron had agreed to meet with Putin.
Putin's last contact with any British official was a brief phone call in June 2007 to congratulate Cameron's predecessor Gordon Brown on his appointment. Cameron has met four times with Russia's President Dmitry Medvedev.
The last visit by a British leader to Russia was Tony Blair's trip to attend a G8 summit in St. Petersburg in 2006. Blair also held meetings in Moscow in 2005.
"It is understandable that there is need for trade and better international relations, but Mr. Putin has blood on his hands," Goldfarb said. "The meeting is a change of policy, and is an endorsement of Mr. Putin, it is very disappointing."
In a joint letter to Britain's Sunday Times newspaper, four former foreign secretaries called on Cameron to press Russian leaders over Litvinenko and on the regime's hostility toward businessmen and journalists, including jailed oil tycoon Mikhail Khodorkovsky.
Last month, BP complained that a Moscow office had been illegally raided after Russian bailiffs accompanied by armed policemen searched its premises in connection with a lawsuit.
Russian officials plan to press Cameron to resume intelligence cooperation, after Britain halted work with security agencies in response to Litvinenko's death.
"We believe that this is in the interests of both countries and in the interests of all countries in the world," Russia's ambassador in London Alexander Yakovenko said.
Yakovenko acknowledged that Britain had shown no indication that it planned to change its stance. "Everything is in the hands of the British side. We are ready," he said.
Jonathan Evans, the head of Britain's domestic intelligence agency MI5, told a committee of lawmakers in a private evidence session last year that Russia and China posed a significant espionage threat in the U.K.
A Russian diplomat was expelled from London in December and accused of spying, while the Russian aide of a lawmaker has been questioned over espionage allegations and faces possible deportation.
Yakovenko warned Cameron that he is unlikely to succeed in pressing Moscow to support a tougher stance on Syria at the United Nations Security Council.
Cameron, who will hold talks Monday with Medvedev and Putin, hopes to encourage trade for British financial and legal services companies, and was joined by representatives from leading law firms.
Trade between the two nations increased by 49.1 percent in the first six months of this year, compared to January-June of 2010, to $10.3 billion. There was an 80.3 percent rise in British exports to Russia, to $3.1 billion, and a 38.7 percent rise in Russian exports to Britain.
Dudley was likely to use the visit to smooth relations between BP and Russia following the collapse earlier this year of a planned Arctic oil deal with state-owned energy company Rosneft - an agreement that had been seen as critical to the company's recovery from the Gulf of Mexico spill.
Rosneft last month agreed a partnership with U.S. company Exxon Mobil to develop offshore oil fields in the Russian Arctic, one of the world's last regions with major untapped hydrocarbon deposits. In return, Rosneft has the option to acquire parts of oil projects in Texas and the Gulf of Mexico.
Lynn Berry in Moscow contributed to this report