About 10,000 pigeons released in a ceremony for China's National Day underwent unusual scrutiny, each having its feathers and anus checked for dangerous materials, state-run media has said, reflecting government concerns over possible attacks.

The symbols of peace were released at sunrise on Wednesday in Beijing's symbolic heart of Tiananmen Square in a ceremony for the October 1 holiday to celebrate the 65th anniversary of the founding of the People's Republic of China.

Beijing domestic security police officer, Guo Chunwei, was quoted in the Jinghua Times as saying workers checked the wings, legs and anus of each pigeon ahead of time to ensure they were "not carrying suspicious material".

The entire process was videotaped, and the birds were then loaded into sealed vehicles for the trip to Tiananmen Square, the newspaper said.

A similar report appeared in the Beijing News, and the People's Daily tweeted about it in English: "10,000 pigeons go through anal security check for suspicious objects Tue, ready to be released on National Day on Wed."

The reports - which did not say what the suspicious materials might be - drew amused and derisive responses from some Chinese readers, and many news sites, including the Beijing News website, later deleted the reports.

However, the Jinghua Times report and the People's Daily tweet were still visible as of midday on Wednesday.

Security worries

The increased security measures reflect heightened concern about violence following a string of attacks blamed on separatist rebels from the country's ethnic Uighur Muslim minority, as well as bus explosions and random slashing attacks attributed to disgruntled individuals.

Last October, three Uighurs in a vehicle rammed through crowds in front of Tiananmen Gate in central Beijing and set off explosives in an attack that killed themselves and three bystanders.

Beijing authorities are also sending police helicopters to monitor highway checkpoints, ring roads within the city, major intersections and areas with heavy traffic, including popular tourist spots such as the Great Wall and the Summer Palace, the Beijing News said.

The capital has also mobilised 850,000 citizen volunteers to help keep a lookout in the city of about 20 million people, the newspaper said.

Source: Agencies