At least 18 people have died after Chinese Muslims attacked police with knives and bombs at a traffic checkpoint in apparent revenge for the government's crackdown on Ramadan.

The attack occurred in the southern city of Kashgar, where tensions between ethnic Uighurs and the majority Han Chinese have led to bloodshed in recent years.

Last week, China inflamed divisions by banning civil servants, students and teachers from fasting during the Muslim holy month and ordering restaurants to stay open.

Suspects killed several police officers with knives and bombs after speeding through a traffic checkpoint in a car in Kashgar's Tahtakoruk district.

Chinese police clash with Uighurs during a protest in Urumqi, the capital of Xinjiang Uighur autonomous region in 2009. A gang of Uighurs attacked a police checkpoint in the southern city of Kashgar this week in apparent revenge for the government's crackdown on the holy Muslim month of Ramadan

Armed police responded by killing 15 suspects 'designated as terrorists', it was reported by U.S.-based Radio Free Asia, which cited Turghun Memet, an officer at a nearby police station.

The attack, which happened on Monday, comes at the beginning of Ramadan, a sensitive time in Xinjiang after a rise in attacks over the past three years in which hundreds have died, blamed by Beijing on Islamist militants.

Repeated calls to the Xinjiang government news office were not answered.

Such incidents are frequently reported in overseas media, but not confirmed by the Chinese government until days later, if ever.

Exiled Uighur groups and human rights activists say repressive government policies in Xinjiang, including controls on Islam and on Uighur culture, have provoked unrest, a claim Beijing denies.

China has banned civil servants, students and teachers in its mainly Muslim Xinjiang region from fasting during the Muslim holy month, which began last week.

The attack occurred in the southern city of Kashgar, where tensions between ethnic Uighurs and the majority Han Chinese have led to bloodshed in recent years

The leading Sunni Muslim seat of learning, Al-Azhar, has condemned China for imposing the restriction.

'Al-Azhar and its grand imam, Ahmed al-Tayeb, condemn the Chinese authorities' ban on Muslims from fasting and practising their religious rituals during Ramadan in some parts of the western Xinjiang region,' said a statement from the Cairo-based Al-Azhar.

'Al-Azhar rejects all forms of oppression practised against Uighur Muslims in China that affect their religious rights and personal freedoms,' said the prestigious institution, demanding that the international community, the United Nations and human rights groups end these violations.

Muslims fast from dawn to dusk during Ramadan, but China's ruling Communist Party is officially atheist and for years has restricted the practice in Xinjiang, home to the mostly Muslim Uighur minority.