(Adds COFCO International; Updates Stada, Calpine)
Aug 18 (Reuters) - The following bids, mergers, acquisitions and disposals were reported by 2000 GMT on Friday:
** U.S. power producer Calpine Corp said it would sell itself to a group of investors led by Energy Capital Partners for $5.6 billion, as the debt-laden company struggles with depressed natural gas prices.
** Yunfeng Financial Group said it would be the main investor in a $1.7 billion acquisition of insurer MassMutual International's Hong Kong unit - a deal that sent shares in the Jack Ma-backed finance firm soaring as much as 30 percent.
** Austrian holiday airline Niki's 850 employees were braced for a bumpy ride as insolvent parent Air Berlin began talks on Friday to sell off its assets before it runs out of cash.
** INTRO-Verwaltungs GmbH, the group controlled by airline investor Hans Rudolf Woehrl, has formally indicated its interest in taking over Air Berlin, it said in a statement.
** Bain Capital and Cinven have won control of Germany's Stada with a sweetened 5.3 billion euro ($6.2 billion) bid for the generic drugmaker, in the largest takeover of a listed German company by buyout firms.
** Elliott Management Corp has quietly ramped up pressure on Energen Corp to explore a sale, according to two people familiar with the matter, as the U.S. oil and gas producer fends off heavy pressure from activist investors to sell itself.
** China's Guangzhou Automobile Group Co Ltd has no plans to acquire automaker Fiat Chrysler Automobiles (FCA) NV , a company spokesperson said.
** CEFC China Energy, which has grown from a niche oil trader to a sprawling energy conglomerate, is in talks to acquire a stake in Russian state oil giant Rosneft, three people with direct knowledge of the discussions said.
** Buyout firms Carlyle and Southern Capital Group are in talks to sell their majority stake in Solusi Tunas Pratama in a deal that could value the Indonesian telecoms tower operator at about $1 billion, three people familiar with the process said.
** Hellman & Friedman LLC is exploring the sale of a stake in HUB International Ltd in a deal that could value one of the largest North American insurance brokerages at between $6 billion and $7 billion, including debt, people familiar with the matter said.
** China's state-owned COFCO International Ltd (CIL) and U.S. farm cooperative Growmark Inc announced the formation of a grain supply partnership which they say will enhance links between U.S. grain production areas and global markets, including China. (Compiled by Roopal Verma and Arunima Banerjee in Bengaluru)