TOKYO, July 29 (Xinhua) -- Japan's automobile production plunged in the first half of this year as key supply chains were severely disrupted and factories were shuttered in the wake of the March 11 twin disasters, the Japan Automobile Manufacturers Association (JAMA) said in a report on Friday.

According to the association, production dropped 29.2 percent in the January-June period of 2011 from a year earlier, totaling just 3,429,934 vehicles.

The figure compares with a 46 percent increase booked in the same period a year earlier.

Output of passenger cars retreated 30.2 percent to 2,925,187 vehicles and truck production dropped 22.4 percent to 464,559 units. A total of 40,188 buses were produced in the reporting period, 27 percent less than the same time a year earlier, JAMA said.

Automobile exports in the first half of the year declined 20.8 percent year-on-year to 1,840,164 units, with sales totaling 59.02 million U.S. dollars, a drop of 10.8 percent compared to the same period in 2010, said the industry body.

The association also noted that overall automobile production retreated 13.9 per cent in the month of June from a year earlier, totaling 742,431 units, with the pace of decline slowing from the 30.9 percent drop booked in May, although still marking the ninth straight month of year-on-year declines.

Production of passenger cars in June declined to 620,717 units, a drop of 16.2 percent, although that of trucks edged up 0.1 percent to total 111,299 units. The output of busses also gained in June, rising 5.5 percent to total 10,485 units produced, said the association.

Domestic sales in June stood at 351,828 vehicles, down 21.6 percent as compared with the same month of the previous year, said JAMA.