Chinese authorities declared Wednesday that the fiery vehicle crash in Tiananmen Square this week was a deliberate terrorist attack and said five men had been arrested for allegedly helping to plan it.

In a statement posted online by the Beijing Municipal Public Security Bureau, Beijing police called the crash that killed five people and injured 40 a “rigorously planned, organized, premeditated, violent terrorist attack.”

Ten hours after the incident — in which an SUV drove through a crowd in the iconic square, then crashed and burst into flames — the five suspects were arrested in a night raid, Beijing police said in a statement on the department’s microblog account that was also distributed by the state-run Xinhua News Agency.

The suspects’ names suggest that they are members of the Uighur ethnic minority from China’s troubled Xinjiang region, a prospect that could heighten already violent tensions between Uighurs and the Chinese government and trigger ever stricter police controls in that part of the country.

The license plate of the crashed SUV was from Xinjiang, police said. Inside the vehicle, police found gasoline, a gasoline container, two long knives, an iron rod and a flag inscribed with extremist religious text.

Police identified the SUV driver as Usmen Hasan and the two passengers as his wife, Gulkiz Gini, and his mother, Kuwanhan Reyim. All three died in the incident.

According to Wednesday’s police statement, Hasan deliberately veered off Changan Avenue, Beijing’s main thoroughfare, and crashed into a guardrail of the Jinshui Bridge, a famous tourist spot in front of the Forbidden City.

He, his wife and his mother then deliberately ignited the gasoline container inside the vehicle and died in the flames, police said. Two tourist pedestrians were also killed, identified by authorities as a woman from the Philippines and a man from China’s Guangdong province.

The crash happened just steps from the famously imposing portrait of Mao Zedong, communist China’s founding father, which hangs from the ancient, red-painted Tiananmen Gate.

The suspects who were arrested told police during their interrogation that they knew Hasan and had “schemed to carry out the violent terrorist act” with him, Xinhua reported. Police said they found flags calling for “jihad” and long knives when the men were taken into custody. Police identified the men as Husanjan Wuxur, Gulnar Tuhtiniyaz, Yusup Umarniyaz, Bujanat Abdukadir and Yusup Ahmat.

One Uighur group expressed immediate doubts about the police investigation, citing its lack of transparency.

“The Chinese government will not hesitate to concoct a version of the incident in Beijing, so as to further impose repressive measures on the Uighur people,” said World Uyghur Congress President Rebiya Kadeer in a statement from Washington on Tuesday night. “Today, I fear for the future of East Turkestan and the Uyghur people more than I ever have.”

A spokesman for the World Uyghur Congress said the organization’s members in China say police have arrested 93 Uighurs since the crash Monday, not just the five suspects whose detention has been announced. “There were no reasons given for the arrests,” said Dilxat Raxit, saying it could mark the start of escalated repression.

Uighurs, a predominantly Muslim ethnic minority, have clashed repeatedly and violently with authorities in Xinjiang in recent years. Uighur groups say they are oppressed by the official policies of China’s authoritarian government and by widespread discrimination within Chinese society. Uighur leaders call the Xinjiang region “East Turkestan” and have called for independence from China and the right to self-govern.

Ethnic rioting and clashes in Xinjiang reached a peak four years ago, causing more than 200 deaths and triggering a crackdown by local authorities. Renewed protests this summer also turned violent and are believed to have claimed more than 100 lives. Monday’s incident, however, marks the first time in the modern era that violence purportedly associated with the Xinjiang clashes has reached China’s capital.

The choice of Tiananmen Square for the attack shows that the perpetrators’ intent was political rather than purely violent, said Lin Zhenlin, an expert on terrorist crime at Beijing’s Renmin University. “Their goal of is to create social panic . . . to press the government to either give them more favorable ethnic policies or for the separatist cause.”

Tiananmen Square was the site of major pro-democracy protests in 1989 that sparked a deadly response by the government, and it is held in reverence by many Chinese, including demonstrators.

The square was built as a symbol of Mao’s power. He proclaimed the founding of the People’s Republic of China from Tiananmen Gate in 1949, and the country’s leaders address crowds and watch parades from that spot on important national holidays.

In 2011, a protester set himself on fire in the square in an incident that was not reported by Chinese media. In 2009, three people whose car was pulled over by police on their way to the square set themselves on fire on a busy Beijing shopping street.

In recent years, fire extinguishers have been placed throughout the square as a safety precaution.

Li Qi and Liu Liu contributed to this report.