Russia's act of aggression in Ukraine has led to the sale of the stake in the Russian oil firm by the British company.
The oil giant was under pressure from the UK government to make the move.
The Russian company has been held by it.
Bob Dudley, a nominee for the board of directors of the oil company, has resigned with immediate effect.
Mr Sechin is a close friend and ally of Russian President Putin, and he was on the board with Mr Looney.
According to the PA News agency, Mr Looney was in Russia in October and appeared on a panel with Mr Putin.
An official said that Business Secretary Kwarteng spoke to the boss on Friday and left him with no doubt about the seriousness of the government concerns.
The attack on Ukraine by Russia was having tragic consequences across the region, and was a fundamental change according to Helge Lund.
It has led the board to conclude that our involvement with the state-owned enterprise simply cannot continue.
This week under heavy political pressure, it became apparent that the share in Russian state oil giant Rosneft was no longer viable.
President Putin has a close ally in the chairman of the oil company. Fuel is supplied to the Russian army.
It was not an option to immediately sell the stake.
The company decided to step back from its two seats on the board and sever its financial ties with the company.
Company officials say it's too early to say how this stake will be sold.
It could be taken away or sold.
It will mean a financial hit for the company, but they had little choice but to pay.
He said that he was shocked and sad by the situation in Ukranian and that it had caused the oil company to rethink its position.
He said that the decisions the board has taken are in the long-term interests of the company.
Mr Kwarteng said that the invasion of Ukraine by Russia must be a wake-up call for British businesses with commercial interests in Russia.
Two weeks ago, the latest annual results were published, and they showed that the Russian oil company accounted for a fifth of its profits.
The multinational, which has its headquarters in London, admitted last year that sanctions on Russia could be problematic for its business and the relinquishing of the Rosneft stake comes after western countries imposed a series of economic sanctions on Russia.
The price of oil hit its highest level in seven years after Russia launched its invasion of Ukraine.
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