Israel elections: Netanyahu challengers Gantz and Lapid join forces

Former IDF chief Benny Gantz (L) and TV-host-turned politician Yair Lapid formed an alliance on Wednesday

Two of Israeli PM Benjamin Netanyahu's strongest challengers in April elections have announced a centrist alliance in a bid to defeat him.

Ex-army chief Benny Gantz and centrist politician Yair Lapid agreed to rotate as prime minister if they win.

Separately, Mr Netanyahu forged an alliance with several far-right parties to try to shore up votes.

His right-wing Likud party leads the polls despite an investigation into corruption allegations against him.

The Israeli attorney general is due to make a decision on whether Mr Netanyahu, who denies the allegations, should be charged in the coming weeks.

Who are the challengers?

Mr Gantz, the former head of the Israel Defense Forces (IDF), and TV-journalist-turned politician Yair Lapid announced their intention to run on a joint centrist ticket on Wednesday, before the Thursday deadline to submit candidate lists for the 9 April elections.

They were also joined by former Defence Minister Moshe Yaalon and ex-military chief of staff Gabi Ashkenazi.

The centre ground agreement is seen as making the race more competitive and a challenge to Mr Netanyahu's decade-long premiership, the BBC's Jerusalem correspondent Tom Bateman says.

Mr Gantz's Resilience party said in a statement that it had "decided to establish a joint list that will comprise the new Israeli ruling party", and vowed to reunite Israeli society.

If successful at the polls, Mr Gantz agreed to hold office as prime minister for the first two-and-a-half years, before Mr Lapid takes over.

Where does Netanyahu stand?

Opinion polls predict Mr Netanyahu's Likud party will win the most parliamentary seats and be in a position to form another governing coalition of nationalist and religious parties.

All governments in Israel are coalitions because of the country's system of proportional representation, meaning a single party is unlikely to be able to govern alone.

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On Wednesday, Mr Netanyahu helped negotiate a merger of the far-right Jewish Home and ultra-right Jewish Power parties, in a bid to boost the total number of seats held by right-wing parties after the polls.

As part of an alliance with his Likud party, he agreed to set aside two cabinet posts for the Jewish Home party, as long as it agreed to the merger.

However, his critics decried the move to join forces with Jewish Power, which includes disciples of the late anti-Arab extremist rabbi Meir Kahane.

The US-born rabbi led a right-wing fundamentalist group in the 1980s that advocated attacks on Arabs, and was later outlawed under Israeli anti-terrorist legislation.

Mr Netanyahu's campaign has been overshadowed by the possibility of the attorney general accepting police recommendations to indict him on suspicion of committing fraud and bribery in three cases.

The prime minister has vowed to remain in office whatever the outcome of the attorney general's decision.

If he wins, he will be on course to become Israel's longest serving leader, taking over that title from David Ben-Gurion.