The Dominican Republic shut all land, air and sea borders with Haiti on Friday in a dispute about construction of a canal on Haitian soil that taps into a shared river, as armed Dominican soldiers patrolled entry points and military planes roared overhead.

Flights were canceled and border towns usually teeming with vendors and Haitians crossing daily to work in the Dominican Republic were subdued. Crowds of people on the Haitian side gathered under the shade of trees as they observed the scene on Friday. Nearby, a white flag fluttered in the breeze under a Haitian flag in a sign of peace.

It was unclear how long the rare closure of the borders will last, with Dominican President Luis Abinader saying the measure will remain in place 鈥渁s long as necessary.鈥� The country鈥檚 Ministry of Foreign Affairs said in a statement that the canal project violates a 1929 treaty and 鈥渕ust be halted immediately before pursuing any other dialogue.鈥�

Abinader ordered his administration to buy all perishable goods normally exported to Haiti, including chicken, onions, beans and eggplants. The food will be used for government programs that offer free meals to students and others, according to Joel Santos, minister of the presidency.

鈥淧roducers should know that the government is going to support them in this situation, because the measure taken by the president represents an issue of security and defense of national sovereignty,鈥� he said.

The diplomatic crisis began earlier this month when workers in Haiti resumed construction of a canal near the Massacre River that runs along the border, to help alleviate a drought that hit Haiti鈥檚 Maribaroux plain. The river is named after a bloody clash between Spanish and French colonizers in the 18th century, and was the site of a mass killing of Haitians by the Dominican army in 1937.

Abinader says the canal will divert water and negatively affect Dominican farmers and the surrounding environment, while Haiti鈥檚 government insists that building the canal falls within its sovereign right to decide how to use its natural resources.

The closure will represent a significant economic hit for both countries that share the island of Hispaniola, although Haiti is expected to feel it more acutely.

鈥淚t鈥檚 really a very drastic measure that doesn鈥檛 make sense economically for either the Dominican Republic or Haiti,鈥� said Diego Da Rin with the International Crisis Group. 鈥淭his will clearly have very bad consequences economically in the Dominican Republic, and it will very likely worsen the humanitarian situation mostly in the areas close to the border.鈥�

Haiti is the Dominican Republic鈥檚 third biggest trading partner, with $1 billion in exports to Haiti last year and $11 million in imports, according to the Dominican Republic鈥檚 Export and Investment Center.

Meanwhile, a study by the Dominican Republic鈥檚 Central Bank found that $430 million in informal border trade was conducted in 2017 between the countries. Of that amount, more than $330 million consisted of exports to Haiti.

to discuss the situation, and were still meeting on Thursday when , prompting the Haitian government to criticize what it called a 鈥渦nilateral鈥� decision.

Da Rin called Abinader鈥檚 actions an overreaction and noted that he confirmed last month he is running for re-election, and appeared to be staking out tough stance on migration. 鈥淢aybe Abinader thinks this is a way to portray himself as a strong nationalist leader who will be the only one 鈥� able to really stop the 鈥楬aitian invasion鈥� as he always calls the growing migration influx.鈥�

On Friday, Haiti鈥檚 Support Group for Returnees and Refugees condemned Abinader鈥檚 moves, and said the canal work should continue.

鈥淐losing the border will bring big consequences for Haitian migrants,鈥� coordinator Ketia Bront茅 said.

She warned that more people are going to cross the border illegally and that the number of cases of human trafficking and contraband would likely increase.

鈥淗aiti and the Dominican Republic are two nations whose history is intertwined,鈥� she said. 鈥淭heir destiny is linked to living together on an island.鈥�

Abinader announced this week that he has . He also has pushed to limit the number of Haitians migrating to the Dominican Republic and . Bront茅 noted that in August alone, some 22,000 Haitians were deported 鈥� twice the usual monthly number.

The Dominican Republic also has started building a 118-mile (190-kilometer) wall along the Haitian border that he announced early last year.

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