UPDATE 1-Strike, vacation hit July sales of Hyundai, Kia

(Adds milestones, background, share prices)

* Hyundai's total sales grow slowest pace since March 2011

* Hyundai, Kia overseas sales lowest levels in 11 months

* Hyundai shares up 0.21 pct, Kia up 0.13 pct in market down 0.11 pct

SEOUL, Aug 1 (Reuters) - South Korean carmaker Hyundai Motor saw its monthly global sales expand at its slowest pace in 16 months in July, as two-day, partial walkout by its domestic factory workers, along with summer vacations, hurt production.

Hyundai Motor, the world's fifth-biggest carmaker along with Kia Motors, posted a 3.1 percent rise in sales at home and abroad in July from a year earlier, the lowest gain since March 2011 when the growth rate was 1.7 percent.

Hyundai and Kia Motors also saw their overseas sales fall to their lowest levels in 11 months.

Workers at Hyundai Motor in South Korea staged their first strike in four years on July 13 and July 20 as annual wage talks stalled amid disagreements over scrapping overnight shifts and other matters.

South Korean factory workers at Kia Motors and General Motors also joined the two-day partial walkouts led by umbrella Metal Workers Union. GM's Korean unit saw its sales fall 9 percent here and overseas in July.

Auto industry wage negotiations have been adjourned for the summer vacation which for Hyundai is from July 29 to August 5.

Domestic sales of Hyundai and Kia also remained sluggish, with their sales remaining almost flat from a year earlier at their captive, home market.

South Korea's car industry association last month cut its 2012 outlook for domestic vehicle sales by 4 percent, as Europe's debt crisis takes a toll on the Asia's fourth-biggest economy, sapping demand from consumers already struggling with heavy household debts.

South Korean exports in July suffered the worst showing in nearly three years and manufacturing activity shrank at its sharpest pace this year, data showed on Wednesday, underscoring how the export-driven South Korean economy was losing momentum more quickly than had been expected.

In the first half, South Korea's domestic car sales fell 4.2 percent to 757,353 vehicles from a year earlier.

Shares in Hyundai Motor ended up 0.21 percent and Kia shares inched up 0.13 percent in the broader market that slipped 0.11 percent. (Reporting by Hyunjoo Jin; Additional reporting by Iktae Park; Editing by Eric Meijer)