BEIJING: Chinese police on Tuesday banned explosives from being transported in the western region of Xinjiang, the scene of deadly ethnic rioting this summer, while more suspects were being investigated for a spate of mysterious syringe attacks.

The Xinjiang Public Security Ministry said transport of weapons, ammunition, explosives and radioactive goods into or within Xinjiang would be suspended from Sept. 25 to Oct. 8.

The ministry did not give a reason, but the dates cover the 60th anniversary of Communist rule in China on Oct. 1 and the holiday period afterward. The ruling party has launched a nationwide security clampdown aimed at making the anniversary pass smoothly.

The notice comes amid ongoing police investigations into reported needle attacks in the regional capital of Urumqi that began Aug. 20 and apparently ended earlier this month. News of the attacks triggered massive street protests by frightened residents demanding better security.

Police had detained 75 suspects allegedly involved in the hypodermic stabbings as of Tuesday, the official Xinhua News Agency said Tuesday, citing a senior police officer.

Huang Yabo, a senior officer with the regional public security department, said police also cracked seven criminal rings and 36 needle attack cases in Urumqi and other cities in Xinjiang including Hotan, Turpan, Kashgar, Changji, Aksu and Altay, according to Xinhua.

Urumqi has been on edge since riots in July left nearly 200 dead in violence between Han Chinese and Uighurs, a minority Muslim ethnic group that is native to Xinjiang. The violence started when a group of Uighurs gathered in Urumqi to protest the deaths of two Uighurs at a factory in southern China.

Authorities blame the July violence and the needle attacks on people trying to split Xinjiang from China, but have not publicized evidence to support that allegation.

On Saturday, the Intermediate People's Court in Urumqi sentenced three people — all ethnic Uighurs — to up to 15 years in prison in the first trials over the attacks. One person was sentenced for stabbing a woman and the other two for using a syringe to rob a taxi driver.

More than 500 people complained of being randomly stabbed by hypodermic needles, but only 171 people showed evidence of being pricked, and tests of samples from victims found no evidence of transmitted infections, Xinhua said.

Uighurs are culturally distinct from China's majority Han group who dominate life in Urumqi and positions of power, despite the fact that Uighurs make up the majority of the population in the wider region of Xinjiang.

Authorities are also looking for dozens of people allegedly involved in the July riot. The China Daily newspaper said Tuesday 825 suspects have been detained and 196 have formally been arrested for their alleged role in the riots.