Operations would be suspended for three weeks at the end of May at BP's West Azeri platform, she said.

A source at the Azeri state energy company SOCAR also told Reuters about planned maintenance at another platform in the Caspian Sea at the end of this month.

Crude oil and condensate production in Azerbaijan rose to 10.6 million tonnes in the first quarter of 2015 from 10.4 million tonnes in the same period last year.

Rising oil output at the main Azeri, Chirag and Guneshli (ACG) oilfields operated by BP had been the reason for the overall increase.

Crude oil and condensate production in Azerbaijan fell to 41.9 million tonnes last year from 43.1 million tonnes in 2013. Natural gas output was 29.2 billion cubic metres (bcm) in 2014.

Falling output at the ACG oilfields has been a cause of concern in Baku.

BP and its partner, SOCAR, tried to calm those worries in 2013, saying production had stabilised. Total oil output rose in 2013 for the first time since 2011, but the decline resumed last year.

Azerbaijan plans to produce 40.3 million tonnes of oil and 29 bcm of gas in 2015.

(Reporting by Nailia Bagirova; Writing by Katya Golubkova and Margarita Antidze; Editing by Mark Potter)