UPDATE 1-Argentina's 2nd-qtr unemployment rate falls to 8.7 pct

(Adds details from report, economic and political context)

BUENOS AIRES, Sept 14 (Reuters) - Argentina's unemployment rate fell to 8.7 percent in the second quarter, the government's Indec statistics agency said on Thursday, down from 9.3 percent in the second quarter of last year and 9.2 percent in the first quarter of this year.

The drop was the latest piece of positive economic news for President Mauricio Macri's market-friendly "Let's Change" coalition as it heads into legislative elections in October. An improving economy could give his candidate a boost over former populist President Cristina Fernandez in a key Senate race.

The fall in unemployment comes after data last month showed the economy grew a cumulative 1.6 percent in the first half of 2017, continuing its recovery from a 2.2 percent contraction last year. Industrial output has grown for three straight months after 15 consecutive months of declines.

Thursday's data marked the fifth time Indec published unemployment data since Macri took office in December 2015 and revamped the agency because of allegations of manipulation under the Fernandez administration. It marked the first year-over-year comparison available during his term.

In districts in the sprawling suburbs of Buenos Aires where Fernandez is facing off against Macri's former education minister, Esteban Bullrich, unemployment fell to 10.9 percent. That compared with 11.2 percent in the second quarter of last year and 11.8 percent in the first quarter of this year.

Despite the fall in the unemployment rate, the economically active population fell to 12.48 million, from 12.50 million in the same period last year. (Reporting by Luc Cohen; Editing by Diane Craft and Steve Orlofsky)