* Brazil"s real leads declines among Latam FX * Colombian stocks jump 2% as Ecopetrol rallies * Dollar gains as Treasury yields rise (Adds comments, updates prices throughout) By Susan Mathew and Shreyashi Sanyal Sept 27 (Reuters) - Latin American currencies fell against a firmer dollar on Monday, while a near 5% jump for oil major Ecopetrol put the Colombian equity benchmark on course for its best session in nearly six weeks. The dollar perked up on rising Treasury yields and after upbeat U.S. durable goods data. Brazil"s real fell 0.7%. The currency is down almost 3% so far this year, as political uncertainty outweighed headwinds from an aggressively hawkish central bank. Worries about policy moves by President Jair Bolsonaro leading up to elections next year have increased as his popularity plummets. "Public debt dynamics in several large EMs, most notably Brazil and South Africa, look particularly worrying – and have been made worse by the pandemic," said William Jackson, chief emerging markets economist at Capital Economics. Brazil"s central bank late on Friday said it would hold additional twice weekly auctions of traditional currency swaps, starting Sept. 27, to address demand from banks dismantling their "over-hedge" position to protect against exchange rate fluctuations. Stocks in Sao Paulo edged 0.3% lower with oil stocks in the lead as crude prices rose amid supply concerns. Oil giant Petrobras rallied around 2%. The Bovespa index is down about 5% this year compared with a 2% slide in the broader EM shares index Mexico"s IPC index, up 0.8% on Monday, has gained about 17% in 2021. Cement maker Cemex rose 2.6% after rating agency S&P revised its outlook to positive from negative. Colombia"s COLCAP index jumped 2.5% to a two-week high as Ecopetrol looked to log its biggest gain in five weeks. Ecopetrol"s crude oil exports to Asia are seen rising, the company"s chief executive said on Monday. Some 63% of the oil firm"s crude exports have been shipped to Asia in 2021, compared with 52% last year. The moves in Latam equities were in line with most other EM shares on Monday, which climbed as hopes rose that Beijing would step in to limit the fallout from debt-laden Chinese developer Evergrande. Key Latin American stock indexes and currencies at 1931 GMT: Stock indexes Latest Daily % change MSCI Emerging Markets 1266.77 0.13 MSCI LatAm 2292.78 -0.17 Brazil Bovespa 113046.16 -0.21 Mexico IPC 51525.80 0.82 Chile IPSA 4351.14 -0.6 Argentina MerVal 75607.11 1.924 Colombia COLCAP 1343.77 2.63 Currencies Latest Daily % change Brazil real 5.3786 -0.65 Mexico peso 20.0751 -0.17 Chile peso 792.5 0.05 Colombia peso 3835 -0.08 Peru sol 4.1173 -0.47 Argentina peso (interbank) 98.6300 -0.04 Argentina peso (parallel) 183.5 1.36 (Reporting by Susan Mathew and Shreyashi Sanyal in Bengaluru; Editing by Alistair Bell and Jonathan Oatis)