July 19 (Reuters) - Sri Lankan shares closed higher for a third straight session on Tuesday, supported by gains in financial stocks.

* At the close of trade, the CSE All-Share index was 1.43% higher at 7,644.12.

* LOLC Development Finance Plc and Ceylinco Insurance Plc were the top gainers on the index, advancing 7.9% and 9.6% respectively.

* Sri Lanka's main opposition leader withdrew from the presidential race on Tuesday and promised support to a low-profile politician from the ruling party who will take on acting president Ranil Wickremesinghe in a tight contest.

* Six-time prime minister Wickremesinghe took over as acting president after a popular uprising amid a devastating economic crisis forced Gotabaya Rajapaksa to flee to Singapore and resign.

* The island nation of 22 million is currently facing its worst economic crisis in seven decades, unable to pay for essential imports such as fuel and medicine due to a severe shortage of foreign exchange.

* The political turmoil comes amid negotiations with the International Monetary Fund (IMF) over a rescue plan.

* Wickremesinghe said on Monday that the country had almost concluded negotiations with the IMF, a day after he declared a state of emergency.

* On the CSE All-Share index, trading volume rose to 66.8 million shares from 65 million shares in the previous session.

* The equity market turnover was 1.12 billion rupees ($3.13 million), down from 1.41 billion rupees in the earlier session, according to exchange data.

* Foreign investors were net buyers in the equity market, purchasing 138.9 million rupees worth of shares, while domestic investors were net sellers, offloading 982.9 million rupees worth of shares, the data showed.

* For a report on global markets, click ($1 = 358.0000 Sri Lankan rupees) (Reporting by Rama Venkat in Bengaluru; Editing by Shailesh Kuber)