May 29 (UPI) -- Four Chinese coast guard ships were seen areas adjacent to Japan-claimed territorial waters, according to a Japanese press report.
NHK reported Tuesday the boats were seen near the disputed Senkaku Islands, or Diaoyutai in China.
According to Japan's coast guard's 11th regional headquarters, based in Okinawa, the boats were seen at 7 a.m. in waters adjacent to Uotsuri-shima.
The coast guard ships were again seen at 3 p.m. in an area about 20 miles roughly northeast of Kuba-shima.
Surveillance is ongoing so as to prevent Chinese vessels from coming near Japanese territorial waters, Japan's coast guard stated.
The monitoring is taking place less than a week after four ships of the Chinese coast guard sailed into Japanese territorial waters for about two hours.
On Thursday, the Chinese vessels entered waters near Uotsuri-shima and waters about 19 miles from Minami Kojima.
The recent round of incursions began on May 18.
Japan's foreign ministry complained to the Chinese embassy in Tokyo in response to the maritime forays near Japan-claimed territory, but the move comes at a time when China and Japan appear to be increasing cooperation.
Information ministers from the two countries and South Korea met Monday to discuss ways to boost exchange, according to The Korea Herald.
Topics of discussion included artificial intelligence, fifth-generation networks, the Internet of things and big data, according to the report.