( CNN ) -- Fierce clashes followed suicide bombings and checkpoint attacks Sunday in Yemen , leaving dozens dead as the government fought back in a province largely controlled by terrorist groups , officials said . At least 60 soldiers were killed in action , a Yemeni government official said , and the number of casualties was expected to climb . Dozens of militants were killed , captured and injured , said the official , who asked to remain anonymous because he was not authorized to speak to the media . Earlier Sunday , officials in the southern province of Abyan said 15 militants were killed in the clashes . At least five troops were killed when suicide bombers earlier attacked two military posts in Abyan , where the government has been desperately trying to weaken terrorist groups after they took over large parts of the province last year . The bombers used explosives-laden vehicles to hit posts on the outskirts of Zinjibar and in the town of Dofas , the officials said . In a separate attack , militants killed four soldiers and wounded three others at a checkpoint in the town of al-Kod . Residents said heavy clashes with militants erupted Saturday night in all three locations . Air raids were not enough to stop the militants from expanding and taking over two checkpoints in Dofas in addition to the three sites they attacked . `` The attacks were fierce against government forces . They used large amounts of heavy artillery , and this is not normal , '' said a senior security official in the province . The official is not authorized to talk to media and asked not to be named . `` Casualties are high from both sides , and this month will be decisive in our fighting against these militant groups , '' the official said . Officials blame the attacks on Ansar al-Sharia , a group with links to al Qaeda in the Arabian Peninsula , the global terrorist network 's branch in Yemen . The attacks come less than a week after President Abdurabu Mansur Hadi took office and days after he changed top civilian , law enforcement and military officials in southern Yemen . The al Qaeda-linked attacks seem to be aimed at sending a message to the new administration , the Yemeni government official said . Ansar al-Sharia fighters are also close to taking over the strategically important military base 115 on the outskirts of Zinjibar , the security officials said . Clashes have been intense near the base since Saturday morning , with little resistance from the government or air support . The site has been vital in the government attempts to uproot the militant group from the province since clashes started in May . Witnesses told CNN that Ansar al-Sharia also cut off a main road linking the provinces of Abyan and Aden . `` Everyone who is traveling between the provinces would easily notice that al Qaeda is in control of the area , '' said Marwan Abdullah , a resident of Abyan who was heading toward Aden on Sunday . Three senior security officials in Abyan accuse Mahdi Makwalah , the military commander of the southern regions , of handing over heavy artillery to al Qaeda fighters Sunday . Last Thursday , Hadi issued a presidential decree ordering Makwalah to step down from his post , but the powerful military commander has so far refused to do so . Among the weapons that al Qaeda fighters were given are nine tanks and heavy artillery , the officials told CNN . `` The only reason why al Qaeda is expanding in Abyan is because they are receiving aid from corrupt officials within the Yemeni government . This is the sad truth about the war on terror in Yemen , '' a security official in Abyan told CNN . CNN 's Jamie Crawford contributed to this report .
NEW : Yemeni official : At least 60 soldiers are killed in the fighting . Fierce clashes erupt as the government fights back . Militants are close to taking over a strategically important base , officials fear . Ansar al-Sharia fighters control important roads , residents say .