BP chief executive Bob Dudley told employees on Monday that investors' patience was wearing thin, as his turnaround failed to show rapid results and the oil giant continues to face headwinds.

Dudley wrote to employees, in an email obtained by Reuters, after a series of problems in recent weeks, including its Moscow offices being raided, its replacement by rival Exxon Mobil in a key Arctic venture, and incorrect reports the Macondo well in the Gulf of Mexico was leaking again.

Investors are interested in clarity and certainty ... I know the time since the Deepwater Horizon event has been frustrating for shareholders, Dudley said.

Analysts had predicted a quick recovery in BP shares after it capped Macondo, which caused the U.S.'s worst ever offshore spill last year. However, BP stock is below the level it traded at when the oil stopped spewing.

Investors and analysts have questioned whether Dudley has a strategy that can lead to growth, after the company's oil production plummeted in the wake of the spill, partly due to asset sales to foot the bill.

Dudley said deals signed this year would allow BP to stop the slide in its core oil and gas production unit. In the upstream we have had our best year in a decade. We have entered into more than 50 blocks around the world.

(Reporting by Tom Bergin; Editing by Dan Lalor)