More than 10,000 armed police in China’s western Xinjiang region staged a mass rally in the capital Urumqi, state media said, as authorities rolled out a rapid-response air patrol system to quell unrest that the government blames on Islamist militants.

The rally held on Monday, complete with circling helicopters and armored vehicles, was at least the fourth such mass display in the region this year, intended as a show of force after a recent uptick in violence.

Hundreds have died in Xinjiang in the past few years, mostly in unrest between the Muslim Uighur people, who call the region home, and the ethnic majority Han Chinese.

Xinjiang’s Communist Party secretary Chen Quanguo told the ranks of armed police lined up outside Urumqi’s international convention center that they must realize the “grim conditions” facing the region’s security.

“Bury the corpses of terrorists and terror gangs in the vast sea of the people’s war,” Chen said, according to the Xinjiang government’s official news site Tianshan Net on Tuesday.

At an Urumqi airport later that day, Chen dispatched 1,500 armed police to the “frontlines” in the Xinjiang cities of Hotan, Kashgar and Aksu.

Those cities, which have seen their own mass rallies in recent weeks, are part of the region’s southern Uighur heartland, where recent violence has flared. Three knife-wielding attackers killed five people and injured five others before being shot dead in Hotan this month.

People’s Armed Police (PAP) and military helicopters, as well as 10 civilian aircraft, carried the forces as part of an “all new” air-land mechanism that would bring high-speed armed helicopter patrols anywhere over Xinjiang’s vast and rugged territory, a notice posted to the Ministry of Defence’s website said. It did not give further details on the patrols.

The PAP is a specialist branch of paramilitary police akin to soldiers tasked with safeguarding domestic security and responding to riots, terrorist attacks and other emergencies.

The air patrols have been rolled out along with a string of new measures in the ethnically divided region, including mandatory satellite tracking devices for vehicles in some areas, and increased rewards for anti-terror tips.

State media that Xinjiang’s spending on public security jumped 19.3 percent in 2016 to more than 30 billion yuan ($4.37 billion).

Rights groups and exiles say anger at tightening Chinese controls on the religion and culture of Uighurs is to blame for violence in the region, though China routinely denies any repression.

(Reporting by Michael Martina; Editing by Michael Perry)