Somali journalists have walked out of a radio station recently seized by Islamists in the capital, Mogadishu. The staff at GBC said they refused to take orders from Hizbul Islam militants. Previously, Hizbul Islam had allowed private radios to operate in their territory, only banning music, which they regard as unIslamic. In Mogadishu, at least 19 people have been killed in heavy fighting, ahead of a crisis summit on Somalia at the UN. UN chief Ban Ki-moon called for the meeting in New York to discuss the deepening political and security crisis. Earlier this week, the prime minister resigned from the weak UN-backed transitional government led by moderate Islamist President Sheikh Sharif Ahmed. The government, backed by a 6,000-strong African Union force, controls only small parts of the capital. Shelling The BBC's Mohammed Olad Hassan in Mogadishu says 19 people have been killed in the clashes that began on Thursday morning. Some 68 people have also been injured as government soldiers, aided by African peacekeepers, battled Islamist militants in the north and south of the capital. There has also been heavy shelling into the central Bakara market. Correspondents say radio stations provide a vital source of information for Mogadishu residents, who need to be constantly updated on which areas are unsafe. The journalists from GBC, which was popular for its broadcasts of international football matches, said they had been ordered to refer to the government as "apostate". "We defied because we do not want to lose our impartiality," one of the reporters said, asking not to be named for security reasons. A newly established free media group Federation of Somali journalists has condemned Hizbul Islam's interference. "It is unacceptable and part of the ongoing violations against the independence and the impartiality of the private media," said its deputy chairman Abdi Haji Gobdoon. Last year nine journalists were killed in Somalia - the highest total in any one year since 1991, when armed conflict broke out following the collapse of the government of the former President Siad Barre. Insurgents from the al-Qaeda linked al-Shabab group have recently intensified their campaign, and along with Hizbul Islam, controls much of south and central Somalia. Source: BBC