BENGHAZI, Libya (Reuters) - East Libyan forces battled to advance into a final area of Benghazi controlled by their opponents on Tuesday, clearing mines and roadblocks and targeting snipers with cover from tank rounds.

Khalifa Haftar’s self-styled Libyan National Army (LNA) says it is close to concluding a three-year campaign for control of Libya’s second city, having surrounded rival fighters in a strip of the seafront district of Sabri little more than two km (1-1/4 miles) wide.

The campaign has been halting, with the LNA suffering high casualties even after gaining the upper hand early last year.

A medical source said at least 17 troops had been killed and at least 50 wounded in fighting since Monday. The LNA said it had killed 19 of its opponents.

“The special forces and supporting units from the army advanced today and tightened the grip on the terrorist groups on the Sabri front, gaining control over important sites,” said special forces spokesman Milad al-Zawi. He said one of the sites was a building that contained a large number of snipers.

Parts of Benghazi have been left in ruins since Haftar launched his “Dignity Operation” against Islamists and other opponents in May 2014.

Many of the buildings in Sabri and the neighboring historic neighborhood of Souq al-Hout have been wrecked by street fighting, shelling and air strikes. Much of the area was heavily mined.

Three years ago Libya split into two broad and shifting rival alliances based in the east and west of the country, loyal to competing governments, worsening the turmoil that followed a 2011 uprising that ousted veteran ruler Muammar Gaddafi.

Haftar’s LNA has gained ground in Benghazi and other parts of eastern and southern Libya while rejecting a United Nations-backed government that arrived in the capital, Tripoli, in March 2016.