Russians attempting to enter the United States at the Mexican border are frustrated that they are not being admitted as easily as Ukrainians, despite having fled their homeland due to the invasion of Ukraine.

Hundreds of Ukrainians have been allowed to enter the United States this week, but Russians are still stuck, prompting some to camp on the pavement alongside a barbed wire border fence, defying Mexican authorities’ orders to leave.

Irina Zolkina, a math teacher who left Moscow with her four children and her daughter’s boyfriend, burst into tears on Thursday when a U.S. border agent looked at her stack of Russian passports and shook his head, saying they would have to wait – soon after officials ushered in six Ukrainian men.

“We’ve been living in fear for so many years… it’s awful inside Russia as well,” she told Reuters in Tijuana, Mexico, near San Diego, California.

Zolkina showed Reuters a BBC video of her arrest on Feb. 24, the day Russia invaded Ukraine in what the Kremlin calls a “special military operation” that Western allies have condemned.

She was released a few hours later and left Russia with her children the following week, she said, passing through Tashkent and Istanbul before reaching the Mexican beach resort of Cancun – a common jumping-off point for Russians heading to the U.S. border.

Over 3 million Ukrainians have become refugees, according to the United Nations, most of them in countries bordering Ukraine. Thousands of Russians have also left their country, according to media reports.

Some Ukrainians crossing in Tijuana have been granted permission to stay in the United States for a year.

When asked on Thursday about Ukrainians and Russians at the border, U.S. Homeland Security Secretary Alejandro Mayorkas said the government was helping people fleeing Ukraine, and that other programs were being considered to expand humanitarian aid.

The U.S.-Mexico border has been closed to most asylum seekers under a coronavirus pandemic policy.

A Department of Homeland Security spokesperson, asked about current policy towards Russians, said the agency makes exceptions to the order on a case-by-case basis for “particularly vulnerable individuals.”