Burundi’s import bill rose 40 per cent in the first quarter of this year from the same period last year, driven by fuel and mechanical spare parts imports, the central bank said on Thursday.The central African nation, which relies on coffee and tea for 85 per cent of its export earnings, has an acute imbalance between exports and imports.Imports totalled 235.9 billion francs ($168.1 million), up from 168.4 billion francs in 2011. Export revenues rose 5.1 per cent to $22.4 million during the first quarter of this year.It said that petroleum products and spare parts for vehicles accounted for more than half of overall imports by volume.The total cost of imports also grew in value due to a weaker franc against the dollar, said the central bank in its report.Burundi’s franc depreciated 34 per cent against dollar in the quarter under review from the same period a year ago.The central African nation’s government expects economy to grow 4.8 percent this year against a 4.2 percent expansion in 2011, thanks to an improved business climate.