On her first day at Basra University this year a man came up to Zeena, a 21-year-old Christian woman, and three other Christian girls and ordered them to cover their heads with a hijab, or Islamic headscarf.

“We didn't listen to him, and thought he might just be some extremist student representing only himself,” she said. The next day Zeena and two of her friends returned to class with uncovered heads.

This time a man in the black clothes of the Shia militia stopped them at the entrance and took them aside. “He said, 'We asked you yesterday to wear a hijab, so why are you and your friends not covering your hair?'. He was talking very aggressively and I was scared,” Zeena recalled.

The girls explained that they were Christians and that their faith did not call for headscarves. “He said: 'Outside this university you are Christian and can do what you want; inside you are not. Next time I want to see you wearing a hijab or I swear to God the three of you will be killed immediately',” Zeena recalled. Terrified, the girls ran home. They now wear the headscarf all the time.

In the past five months more than 40 women have been murdered and their bodies dumped in the street by militiamen, according to the Basra police chief. Major-General Abdul-Jalil Khalaf said that some of them had been killed alone, others gunned down with their children. One unveiled mother was murdered together with her children aged 6 and 11.

The British Army will formally hand Basra over to Iraqi control in less than two weeks, claiming that it had done all it could to stabilise the southern port city during four years in charge. Yet as a tentative stability returns to Baghdad, where even alcohol shops are starting to reopen, Britain appears to be leaving Basra ever more firmly in the hands of lawless gangs and strict morality police.

Messages are scrawled in graffiti warning women not to venture out without observing Islamic dress codes. “Whoever disobeys will be punished. God is our witness that we have conveyed this message,” says one scrawled in red paint on a wall. A huge advert for mobile phones, featuring a mother and child, has been defaced to blot out the uncovered woman's head with the slogan “No, no, to unveiled women” sprayed below.

At the university, Sunni students complain of being harassed by Shia militias. Ahmed, a 19-year-old Sunni freshman, was told that he had to grow a beard but keep his hair short to adhere to Islamic norms. He said that boys and girls who try to sit next to each other will be told to stay apart and given a lecture on Islamic virtue.

Self-appointed morality police, similar to the Bassiji who haunt students across the border in Iran, also grab people's mobile phones and scroll through them looking for “immoral” video clips, music or pictures, Ahmed said.

Another student, Ali Yusuf, said that militiamen halted a freshers' week party for new students, turning off the music system and ripping down the decorations. One armed thug picked up the DJ's microphone and started praising Hojatoleslam Moqtada al-Sadr, the fanatical cleric who leads al-Mahdi Army, the most powerful Shia militia, before reading out a list of rules.

Despite Basra's increasing similarity to the repressive Iranian theocracy, which many believe has exerted it influence over the city, Britain says that its work here is done, and plans to reduce troop levels to only 2,500. Critics say that will barely allow the Army to protect its own base at Basra airport.

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