Israeli Prime Minister Ehud Olmert addresses the Israeli Cabinet
Israeli Prime Minister Ehud Olmert has submitted his resignation letter to the country's President, Shimon Peres.
Mr Olmert may remain as interim prime minister for several weeks while his successor as leader of the Kadima Party tries to form a new government.
He is to be replaced by Israel's Foreign Minister Tzipi Livni, who has six weeks to gather a fresh coalition.
Mr Olmert announced he would step down in July after facing growing pressure over multiple corruption inquiries.
The BBC's Wyre Davies in Jerusalem says that forming a coalition will not be an easy task as Kadima does not have a majority in the Israeli parliament, known as the Knesset.
The same parties, particularly religious parties from the right, who joined the Olmert government will not necessarily support Ms Livni, our correspondent says.
It is a complicated process that may end in general elections at the start of next year, until when Ehud Olmert may remain as prime minister, our correspondent adds.
Ms Livni, who is regarded as a moderate, won the leadership of the governing Kadima party on Thursday, beating Transport Minister Shaul Mofaz by just 431 votes, or 1.1%.
According to the president's office, Ms Livni will have up to 42 days to attempt to form a coalition representing at least 61 of the Knesset's 120 seats from Israel's mosaic of political parties.
If she fails, the president may give another member of the Knesset up to 42 days to try to form a government.
If still no government is formed, the president may mandate yet another member to try, or call elections, which must then take place within 90 days.
Mr Olmert has faced growing pressure over multiple corruption investigations during his less than three years in office. He denies any wrongdoing in all cases.
Police have recommended he be indicted over two of the probes - allegations that he misused cash payments from a US businessman, and accusations that he double-billed government agencies for trips abroad.
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