HANOI, July 11 (Xinhua) — The Vietnamese foreign ministry has sent a diplomatic note denouncing shooting at Vietnamese fishing boats and urged Thailand to probe the incident.

The Thai navy opened fire on three Vietnamese fishing boats with 18 fishermen on board, according to the Vietnamese Embassy in Thailand.

The firing, at around 14:00 local time (0700 GMT) on Friday, injured two fishermen and left another missing while two of the boats sank in collision with Thai naval vessels.

The fishing boats were chased by Thai naval police after they were allegedly found illegally operating in Thai waters, Nguyen Hai Ngoc, first secretary of the Vietnamese Embassy, was quoted by Vietnam's state-run news agency VNA on Monday.

Nguyen Van Teo, 28, who was shot in the right leg, and Nguyen Van Linh, 25, injured in the shoulder, were brought to the shore by Thailand's helicopter while the remaining 15 crew members were taken ashore by Thai naval vessels, Ngoc added.

He noted that the fishermen were in custody at Naval Zone 2 of Thailand's Royal Navy in Songkhla province and expected to stand trial on Monday for illegally intruding into Thai waters and fishing without permission.

However, the diplomat stressed that shooting at foreign fishing boats that violating a country's territorial sea is against international law and practice.

A group of officials from the Vietnamese Embassy have flown to Songkhla to settle the incident.

It was the second time that Thai navy shot at Vietnamese fishing boats.

In September 2015, they opened fire on Vietnamese boats, killing a fisherman.