A woman and her three children were killed early Wednesday when the Shia Houthi militia shelled Enma City -- said to be hosting numerous refugees -- in Yemen's northern Aden province, according to eyewitnesses."A projectile believed to be a Katyusha rocket struck a building on the city's main street, killing the woman and her three children," eyewitnesses told Anadolu Agency."The Houthis and pro-Saleh forces use iftar [Ramadan evening dinner] and the Fajr [dawn] prayer-times, when the Saudi Arabia-led air force is not usually present, to carry out rocket and mortar strikes against residential areas," witnesses added.Yemen's Shia Houthi militia, which since last year has overrun much of the country, remains an ally of forces loyal to former president Ali Abdullah Saleh, who was forced to step down in 2012 following one year of pro-democracy demonstrations.On Tuesday, seven other people were killed -- including two women and a child -- after Houthi and pro-Saleh forces shelled Enma City, according to witnesses.Also on Tuesday, a Saudi-led air coalition carried out 15 separate airstrikes on Houthi positions -- including an airbase -- in western Yemen's Al-Hadida province, local residents said.In late March, Saudi Arabia and its Arab allies began an extensive air campaign that has continued to pound Houthi positions across the poverty-stricken Arab country.