Kazakhstan`s long-ruling President Nursultan Nazarbayev appointed a new prime minister on Monday, his office said, after dismissing the government over a lack of economic development. "The head of state signed a decree appointing (Askar) Mamin prime minister of Kazakhstan," Nazarbayev`s office said on its Twitter account. Mamin, 53, has previously served as first deputy prime minister and also worked as transport and communications minister and mayor of capital Astana. Mamin`s predecessor Bakytzhan Sagintayev was sacked over what Nazarbayev described as poor economic performance, despite the Central Asian nation`s vast energy resources. Sagintayev was viewed by some analysts as part of a potential leadership transition in the country, which 78-year-old Nazarbayev has ruled over for close to three decades. Observers point to rising discontent in Kazakhstan, a former Soviet republic whose commodity-dependent economy has struggled to recover from a 2014 plunge in oil prices. Western sanctions against Russia, a key trading partner, also hit the economy.