Three of the recently flagged matches were at Wimbledon - two in qualifying, one in the main draw - and one was at Roland Garros.
"Every alert is assessed and followed up as an indicator that something inappropriate may have happened", the briefing report reads.
The matches at grand slam level that prompted alerts are the biggest cause for concern, but as usual it is in the lower levels of the game where unusual betting patterns are most rife. There were 73 alerts during the same period a year ago.
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The report also states that the TIU received 53 other alerts between April and June - three of those from the men's ATP tour and one on the women's WTA tour. A number of other factors, such as playing conditions or an injury to one of the players, could account for anomalous betting patterns. The first six months of 2017 has seen 83 alerts raised in total, 38 less than previous year.
Just before the 2016 Australian Open, BuzzFeed and BBC News released reports claiming that match-fixing is widespread at the upper levels of the sport and that a "core group" of players often appear in incidents of suspicious betting but that none had been sanctioned by tennis authorities.
The matches and players concerned have not been disclosed.