A bus carrying Pakistani  pilgrims crashed in central Iran killing at least 28 people on board, state media reported.

Another 23 people sustained injuries, seven of whom are in serious condition, according to an emergency official cited by state-run IRNA news agency.

"Of the 23 injured, six have already been discharged from hospital, while the condition of seven others is critical," Mohammad Ali Malekzadeh said. "The dead consisted of 11 women and 17 men," he added.

He said all 51 passengers on the bus were from Pakistan.

Pakistan's Interior Minister Mohsin Naqvi expressed his condolences, saying: "We are deeply saddened by the loss of precious human lives in the bus accident in Iran."

Where were the pilgrims headed?

Pakistani pilgrims were headed from Iran to Iraq to mark the holy day of Arbaeen — one of the biggest events of the Shiite calendar.

It marks the death of Imam Hussein — who is the grandson of the Prophet Mohammed — and his companions in the Battle of Karbala in 680 AD.

Many Shiites make pilgrimages to a shrine in Karbala, Iraq, which is believed to be Hussein’s tomb.

What do we know about the bus accident?

The bus accident occurred late Tuesday in central Iran's Yazd province due to a technical fault that paralyzed the brakes, according to initial investigations conducted by Iran's traffic police.

Pictures released by Iranian media shows the bus turned upside down with its roof smashed in and all its doors open.

Road accidents are quite common in Iran with some 17,000 deaths annually. The grave toll is blamed on poor traffic laws and a lack of regulations.

mfi/rm (AFP, AP, Reuters)