Negative Wall Street and Footsie close adds to depressed sentiment.
Oil futures rose $0.87 to settle at $51.23 a barrel, the first time it closed above $51 since July 2015.
Military presence reduced in Niger Delta as Buhari rumoured to be in London for secret talk with militants.
Oil futures rose for a third successive session, after a higher than expected drawdown in US crude inventories.
Exports in the world's second largest economy declined 4.1% on-year in May.
Decision to scale back army presence follows threats by new militants as oil production plummets.
Brent August futures traded above $50 per barrel level bucking the decline in US oil inventories.
The US Federal Reserve Chair hinted that the American central bank would not increase interest rates in June.
Nigerian leader has cancelled three official trips in a month.
US nonfarm payrolls employment data showed that 38,000 jobs were created in May.
JNDLF vow missile attack after Avengers blow oil pipelines as renewed violence rocks Niger Delta.
Pipeline attacks continue in restive south-eastern Nigeria as oil production decreases.
Investors awaiting release of US Labor Department's non-farm payroll data for May.
Mohammed Sanusi Barkindo named as new secretary general.
The JPMorgan global manufacturing PMI declined to 50.0 for May, indicating stagnation.
Riyadh reportedly in favour of imposing ceiling on Opec's collective crude output to support weak prices.
EXCLUSIVE: Recorded phone conversation with UK-based station reveals NDA threats to Muhammadu Buhari.
The private Caixin/Markit survey showed that activity at China's factories contracted for the month of May.
Goldman's report says there is a 70% chance that MSCI, will include mainland Chinese shares in its indexes.
Yellen had said that interest rates could be increased in the coming months.
Group condemns perceived marginalisation in Niger Delta and demands greater shares of oil revenues.
Buhari promised he would end corruption and terrorism and revitalise crippled economy.