Vietnamese officials Wednesday condemned protests held by Cambodians near the two countries’ borders that led to clashes between Vietnamese authorities and civilians, leaving more than a dozen people injured. The protests are the latest development underscoring growing tensions at the shared border.

Roughly 250 Cambodian activists, including Real Camerin, a member of the opposition Cambodian National Rescue Party (CNRP), illegally entered Vietnamese territory through a shared border on the eastern part of Cambodia, the Bangkok Post reported. “Vietnamese security officers and local residents tried to reason with the activists and stop them, but they were attacked,” Le Hai Binh, spokesman for the Vietnamese foreign ministry said in a statement on Wednesday. Seven Vietnamese and ten Cambodians were reportedly injured in the confrontation.

The opposition group is known for protesting against close ties between Phnom Penh and Hanoi, and have organized protests along the 1,270 km (about 789 miles) border in the past. The border is not fully demarcated and has caused confusion in the past.

Cambodia’s government officially expressed apologies for the injuries, but CNRP leader Sam Rainsy said that they were “faultless” in the scuffle and urged the Cambodian government to take on “foreigners who look down on Cambodians … and swallow the land.”

The Cambodian protests was thought to have been sparked by allegations that Vietnam has been illegally digging ponds on the Cambodian side of the border and had plans of constructing a military outpost in the area, Voice of America reported.

Binh did not respond to questions regarding those claims during a regular press conference but did have strong words for the protesters. “We strongly condemn the violent activities caused by extremists in Cambodia,” Binh, spokesman said. “The activists violated the legal regulations of both sides, and treaties, agreements signed between the two countries, affecting the process of demarcation as well as the relations between Vietnam and Cambodia.”

Binh added: “We request Cambodian competent authorities to soon have appropriate measures to deal with the incident, prevent similar activities from happening and ensure the work of demarcation for common interests of the two nations.”