BERLIN, July 10 (Reuters) - BMW on Tuesday reported the strongest sales among Germany's top three premium carmakers and was the only brand to significantly boost battery-electric deliveries, as Mercedes-Benz and Porsche struggled with low demand. BMW saw a 2.3% rise in total sales in the first half of the year to almost 1.1 million vehicles, with battery-electric sales surging 34% to a total of nearly 180,000 cars.

Mercedes-Benz sold roughly half as many battery-electric cars at 93,400, a 17% drop from a year ago. Total sales by Mercedes-Benz core brand dropped 6% to 960,000.

"The ramp-up of electric vehicles slowed in key markets, while the company focused on healthy growth in a market environment characterised by heavy discounting," Mercedes said in a statement.

Carmakers have been slashing prices of electric vehicles particularly in China in an attempt to boost sales amid dampened demand and rising competition as carmakers broaden their electric lineups.

Both Porsche and Mercedes-Benz, as well as Volkswagen's premium brand Audi, have said upcoming model launches would help make up lost ground and boost sales. Audi sales fell in the first six months of the year by 8% to 833,000 vehicles, with battery-electric sales up by just 1.3%.

Porsche, which sells a lower volume of higher-priced cars, saw sales drop 7% to just 155,900 vehicles with a particularly steep drop of a third in China.

Analysts said after a pre-close call with Porsche AG executives on Tuesday that revenue should improve in the second quarter from higher availability of top-end models, resulting in a margin in line with forecasts of 15% to 17%.

"We continue to like the stock," analyst Tim Rokossa of Deutsche Bank said in a note. (Reporting by Victoria Waldersee, Ilona Wissenbach, Rachel More; Editing by Miranda Murray and Arun Koyyur)