Apple Inc shares fell 4 percent on Wednesday after the company reported its slowest-ever rise in iPhone shipments, with an uptick likely only after the expected launch of iPhone 7 in September.

The March quarter is likely to be the weakest this year in terms of iPhone sales for the company, which forecast on Tuesday its first quarterly revenue drop in 13 years.

Shares fell to $95.97 at open, knocking off nearly $20 billion from Apple's market value of about $554 billion.

Tepid demand for the latest iPhones - that succeeded blockbuster sales of the iPhone 6 and 6 Plus - led Apple to sell 74.8 million iPhones in the first quarter. It expects to sell 50-52 million units in the March quarter.

But analysts said the depressed stock price could create a buying opportunity for long-term value seekers.

"We are looking for March to mark the trough in year-on-year iPhone unit growth, which should provide an attractive entry point into the stock ...," Goldman Sachs analysts wrote in a note.

At least 11 analysts cut their price targets on the stock. FBR Capital was the most bearish, cutting its target by $20 to $120. The median price target is $142.29, according to Reuters data.

"Cook & Co have a few tough quarters ahead until we get to the buildup around iPhone 7 later this year, which is what bulls (including ourselves) are focused on to turn this ship back into growth waters," FBR & Co analysts said.

Apple usually launches new iPhones in September and sells most devices in the December quarter. Unit sales typically drop over the next few quarters leading up to the next iPhone launch.

The iPhone 7 is expected to sport a new look with features such as waterproofing, wireless headphones and force touch as home button.

Up to Tuesday's close, Apple's stock had lost a quarter of its value since April 28, when it hit a record high of $134.54. In contrast, shares of Alphabet Inc rose 10 percent in the same period. While Apple trades at 10.5 times forward 12-months earnings, Alphabet trades at 25.30.

Reuters (Reporting by Supantha Mukherjee, Tenzin Pema and Tripti Kalro in Bengaluru; Editing by Sayantani Ghosh)