BEIJING (REUTERS) - China's elite Politburo endorsed a crackdown on extremists in Xinjiang on Monday, a day after police said they had smashed nearly two dozen groups in the aftermath of the far western region's deadliest attack in years.

China announced a year-long "anti-terrorism" operation in Xinjiang, home to a large Muslim Uighur minority, as well as nationwide, following a series of bloody incidents that Beijing blames on Islamists and separatists from the region.

China Central Television said the Politburo, a decision-making body of the ruling Communist Party, met under President Xi Jinping and discussed measures to counter extremists in the sprawling region that abuts ex-Soviet Central Asia.

Party leaders, the broadcaster reported, spoke in favour of "upholding ethnic unity" in Xinjiang and preventing the spread of religious extremist ideas.

The meeting underscored the difficulties of China's leadership in reassuring the public of stability in view of the deadly attacks, including a suicide bombing that killed 31 at a market in Urumqi, the region's capital, last week.

Exiles and rights groups say the real cause of the unrest is China's repressive policies that put curbs on Islam and the culture of Uighurs, Muslims who speak a Turkic language. Uighurs have long complained of official discrimination in favour of the Han, China's majority ethnic group.

On Sunday, the official Xinhua news agency quoted Xinjiang's public security department as saying that police had smashed illegal groups in southern parts of the region. More than 200 explosive devices were seized in raids.

Many of those captured were in their 20s and 30s, and had learned to make explosives from online videos, Xinhua said.

"They exchanged their experiences of making explosives and propagating jihad through chatting tools, text messages and illegal preaching sites," the news agency said.

China has said five suicide bombers carried out last Thursday's attack in Urumqi. It was the second attack in the city in just over three weeks, after a bomb went off at a train station in late April, killing a bystander and wounding 79.

At least 180 people have been killed in attacks across China over the past year.

Beijing says separatist groups in Xinjiang are seeking to form their own state called East Turkestan, though experts dispute the influence and reach of the most prominent group, the East Turkestan Islamic Movement (ETIM).