Robbers armed with assault rifles raided a branch of Al-Ahli bank in Aden on Thursday, wounding a banker and a security guard, local media reported, after similar assaults in the southern province.

          "We hope there will be a serious response to the attack and the perpetrators will get arrested and tried," the letter said according to the daily , demanding more protection.

          The city is under the control of the Security Belt, a southern force taking part in a civil war that has killed more than 10,000 people. Cholera and famine have also spread in the impoverished country.

          Aden is nominally the seat of the internationally-recognized government although the president and other cabinet members live in Saudi Arabia for security concerns due to attacks by Islamist militants.

          The letter also said the banks would suspend clearing operations and threatened to take more measures if authorities did not respond by protecting local branches. A copy was also sent to Aden's governor, it added.