Mergers and acquisitions involving Japanese companies have decreased sharply this year as slowing sales and large restructuring costs have eaten into financial resources, according to recent data compiled by leading M&A adviser Recof Corp.

In the first seven months of the year, the number of M&As involving Japanese companies totaled 1,124, down 20.8 percent, with a combined value of ¥3.64 trillion, off 47.3 percent from the corresponding period of last year, Recof said.

In particular, M&As overseas by Japanese companies plunged to one-third of the level a year before.

The biggest deal in the January-July period was clinched by Sumitomo Mitsui Financial Group Inc. in May to acquire operations from Citigroup Inc., including Nikko Cordial Securities Inc., for ¥570 billion.

In July alone, there were 148 M&As involving Japanese companies, down 32.4 percent from year earlier, Recof said.