At least 20 people have been crushed to death in a stampede among people gathering to get free flour in the Pakistani city of Karachi.

At least 18 women and children died as charity workers were overwhelmed with the crowd receiving the gift for the holy month of Ramadan, police said.

Monday's food distribution was in a poor neighbourhood, and Wasim Ahmed, the city's police chief, said that dozens of other people were injured.

Amin Khan, an official in Civil Hospital Karachi, said: "The deaths were caused by suffocation and the stampede in one of the most congested localities of Khori Garden."

The death toll is expected to rise.

Pakistan, a Muslim-majority nation, is observing the Islamic holy month, during which believers fast from dawn to dusk.

'Struggling for life'

Fatima Hashim, a 55-year-old witness whose daughter was seriously injured, said it had occurred in a small area where huge crowds had gathered.

"The place where wheat flour was being distributed was very narrow, which suffocated hundreds of women and children," she said.

"I went along with two of my daughters to get two bags of flour, but now my younger daughter is struggling for life in the hospital."

Another witness, Hafeeza Begum, said: "We were in a long queue waiting for our number [to be called] to get a 10kg bag of flour from the charity when people started running.

"I was quite far from the platform where the bags were being distributed, so I promptly grabbed my teenage daughter and reached a safer place."

Television footage showed images of distraught parents arriving at the Civil Hospital, women and children lying on beds and corpses covered by white sheets.

The flour handout was organised by a private group. Ahmed said that the man distributing the flour had been arrested because he had not given prior notice to the police.

Pakistan's worst stampede in recent memory, killed 29 women and children in April 2006, at a festival to commemorate the anniversary of Prophet Muhammad's birthday, in Karachi.