TRIPOLI, April 4 (Xinhua) -- Libya's eastern-based army commander Khalifa Haftar on Thursday launched a military operation to take over the capital Tripoli, where the UN-backed government is based.

"To our army based around Tripoli from all axes, we continue today our struggle," Haftar said in a statement issued by the army's information office.

"We respond to the call of our people in our capital after they ran out of patience," he added.

Notably, the army commander called for "use of force against only those who fight the army."

A day earlier, the army spokesman announced plans of the army to take over western Libya including Tripoli, hours before the UN-backed government in Tripoli declared a state of public alert against the army's plans.

UN Security-General Antonio Guterres, who arrived in Tripoli on Wednesday, expressed concern over the recent military escalation in Libya.

"There is no military solution. Only intra-Libyan dialogue can solve Libyan problems. I call for calm and restraint as I prepare to meet the Libyan leaders in the country," Guterres said.

Haftar's army is allied with Libya's eastern-based government, as the North African country is politically divided between two governments in the east and west.

Libya has been struggling to make a democratic transition amid insecurity and chaos since the fall of former leader Muammar Gaddafi's regime in 2011.