Thailand began imposing land border restrictions Monday including blocking tourists heading into Cambodia as the two countries engage in retaliation in their border dispute, Associated Press reported.

Relations between the countries have deteriorated following an armed confrontation May 28 in which one Cambodian soldier was killed in a relatively small, contested territory. While the two sides have agreed to de-escalate their dispute, they continue to implement or threaten measures that have kept tensions high.

Prime Minister Paetongtarn Shinawatra said Monday that Thailand will boost screening at land borders and block departing tourists, saying that only students, medical patients and others who need to purchase essential goods would be allowed to enter or leave Thailand.

She said the measures were aimed at blocking people heading toward Cambodia’s lucrative casinos, but it appeared that all tourists would be blocked, according to Associated Press.