A Houthi fighter stands guard as he secures the site of a demonstration by fellow Houthis against the Saudi-led air strikes on Yemen, in Sanaa April 1, 2015.[Photo/Agencies]

About 13 civilians were killed during the random shelling and gunfire in Aden on Thursday, a medical official at Gomhouria hospital told Xinhua.

Security sharply deteriorated in Yemen since early March when conflict erupted in several provinces in the country's southern regions.

The Shiite Houthi group launched attacks on Aden city, which President Abd-Rabbu Mansour Hadi declared as the temporary capital after he fled weeks of house arrest by the Houthis in Sanaa.

Last Thursday, a Saudi-led coalition started airstrikes on Houthi targets in Sanaa and other cities, saying the multinational action was to protect Hadi's legitimacy and force the Houthis to retreat from cities it seized since September 2014.