ADEN, April 2 (Reuters) - Yemeni forces killed seven Islamist fighters in overnight clashes in a southern city, local officials said on Monday, as the army struggled to gain the upper hand against militants emboldened by a year of political upheaval.
A military official said the army shelled parts of the city of Zinjibar in the southern province of Abyan, where militants have exploited weakened central government control to grab swathes of territory and several towns.
Among the dead militants was a Somali, local officials said. The interior ministry last month said Somali militant group al-Shabaab, which is allied to al Qaeda, had sent 300 armed men to join ranks with Islamist fighters in Yemen.
The impoverished state has seen a surge of attacks claimed by an al Qaeda-linked group that calls itself Ansar al-Sharia (Partisans of Islamic Law), which has killed nearly 200 soldiers since President Abd-Rabbu Mansour Hadi took office in February.
In another sign of the declining security in Yemen's south, a local official said militants bombarded a disused military airbase near the port city of Aden on Monday.
"The holy warriors this morning bombarded the Badr military airport in Aden with mortar shells," read a text message purporting to come from Ansar al-Sharia.
The recent spate of militants attacks threatens to overshadow, if not derail, a transition away from the rule of President Ali Abdullah Saleh, who was forced out of office by months of protests against him.
The United States and neighbouring Saudi Arabia threw their weight behind the Gulf-brokered power transfer plan under which he resigned, fearing protracted political chaos would strengthen al Qaeda's Yemen-based wing.