anks in the city of Aden, Yemen, will close for three days from Monday and suspend clearing services in protest after a spate of armed robberies, 12 lenders have said in a letter to the central bank.

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, demanding more protection.

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 of the letter was sent to Aden's governor.

Aden 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 in the Arabian Peninsula country.

Ongoing campaign

A coalition led by Saudi Arabia, and backed by US arms and intelligence, has waged a nearly two-year campaign on behalf of Yemen's internationally recognised government, which the Shia Houthi group - allied with Iran - is battling to dislodge.

The conflict has pitted the government forces of President Abd-Rabbu Mansour Hadi backed by the Arab coalition against the Houthi fighters and their local allies since late 2014.

Aden is nominally the southern power seat of the Hadi government although he and other cabinet members live in Saudi Arabia for security concerns due to attacks by armed groups.

The bank closures come close on the heels of the deaths of five government soldiers in an attack by unknown attackers in the province of Shabwa, local security sources said.

Four other soldiers were injured in Sunday's attack, which targeted a security checkpoint, according to the sources, who spoke to DPA news agency on condition of anonymity.

Shabwa is mostly under the control of Hadi's government.

Al-Qaeda fighters have expanded their influence in parts of Yemen, taking advantage of the strife.

Fighting has intensified in Yemen since March 2015, when the Houthis and their local allies advanced on Aden, prompting Saudi Arabia and fellow Sunni allies to start their air campaign.

Yemen is also struggling to cope with a deadly cholera outbreak that has caused more than 1,700 deaths in the last few months.

The spread of the disease has been facilitated by rising levels of malnutrition, a crumbling economy, and virtually non-existent health, water, and sanitation systems.

In late June, the World Health Organization placed the number of suspected cases at 200,000.

Less than a month later, the International Committee of the Red Cross (ICRC) announced that more than 300,000 are suspected to be ill.

Robert Mardini, the Red Cross regional director for the Middle East, says this number is growing by roughly 7,000 a day, and WHO estimates that half of these cases are children.