BEIJING — Police in China's far west have launched a crackdown on terrorism and stepped up a hunt for suspects who took part in deadly ethnic riots there four months ago, the regional public security ministry said Tuesday.

The "Strike Hard" campaign is to run from November through the end of the year and will cover all of the remote Xinjiang region, with police on high alert for terror plots, the ministry said in a faxed statement.

Hundreds have already been arrested and nine people sentenced to death following the July 5 riots, which saw Uighurs attacking Han Chinese in the regional capital of Urumqi. Nearly 200 people were killed in those attacks and in the revenge killings of Uighurs by Han Chinese in the days that followed.

Uighurs are a Turkic Muslim ethnic group linguistically and culturally distinct from China's majority Han. The Uighurs see Xinjiang as their homeland and resent the millions of Han Chinese who have poured into the region in recent decades. A simmering separatist campaign has occasionally boiled over into violence in the past 20 years.

China says overseas Uighur separatists orchestrated the riots to worsen ethnic divisions and bolster their campaign for independence but the government has provided little evidence to back up its claim.

"We must step up efforts to collect and analyze information and clues regarding terror and explosives in order to strictly prevent occurrences of violent cases of this sort," the statement said, without referring to any particular threats.

It also ordered security forces to continue the search for riot suspects.

The remote oil-rich region has been blanketed in tight security since the violence erupted, with Internet access and long distance phone service cut for even ordinary people.

Overseas Uighur rights activists and human rights groups have accused Xinjiang security officials of illegally detaining dozens of alleged rioters for months without informing families of their whereabouts, with some suspects said to be as young as 14 years old.