UPDATE 1-Israeli PM Netanyahu will sue political rivals for libel

Israeli Prime Minister Benjamin Netanyahu said on Friday he would sue two of his main political rivals for libel over remarks relating to a graft scandal involving a German submarine deal. In a video published on his Facebook page, Netanyahu said he had instructed his attorneys to take legal action against former armed forces chief Benny Gantz and ex-defence minister Moshe Yaalon, both from the centrist Blue and White party which is seeking to unseat the prime minister in an April 9 election.

Netanyahu faces no charges over the submarine deal but he faces possible indictment in three other corruption cases. He has denied all wrongdoing. Netanyahu, a four-term veteran, will become Israel's longest-serving prime minister in the summer if he wins next month's election.

But he faces serious challenges on different fronts. The charismatic Gantz has solid credentials on security, traditionally a strong point for Netanyahu. Polls put Netanyahu’s right-wing Likud and Gantz’s Blue and White party neck-and-neck. Last month Israeli Attorney-General Avichai Mandelblit said he intends to indict Netanyahu in three cases on charges of bribery, fraud and breach of trust, pending the outcome of a pre-trial hearing which will take place after the election.

Gantz has sought to focus public attention on the state’s decision not to deem Netanyahu a suspect in the submarine case. Netanyahu accuses his opponents of carrying out a politically motivated "witch-hunt". (Reporting by Stephen Farrell Editing by Gareth Jones)