BEIRUT – Shelling and explosions were heard in the Syrian capital Damascus throughout Wednesday during some of the fiercest clashes reported in months, as government and opposition forces said they had made significant advances.

An acrid smoke hung over parts of Damascus, opposition activists said.

The renewed fighting in the capital appeared to dash the faint hopes of peace talks in the almost two-year-old conflict. Neither side has agreed on any dialogue, despite conditional offers in recent weeks from representatives of the opposition and the government of President Bashar Assad.

Late Wednesday it was unclear if either side had pushed forward or whether the government and rebels had managed to hold their positions in and around Damascus.

Opposition activists said various rebel militias had launched coordinated attacks early Wednesday on checkpoints and other government-controlled positions in what some termed a final battle for the capital.

“It lit up in Damascus,” said one opposition activist reached via Skype. “It’s a big war inside Damascus.”

The fighting appeared to be concentrated in the vicinity of Damascus’ Abaseen Square, a strategic site near the boundary with the beleaguered eastern Ghouta region and the northeastern suburb of Jobar, which reportedly suffered heavy shelling. But clashes also raged in several southern city neighborhoods and suburbs, according to opposition and official accounts.

The government media office said the military had inflicted “heavy losses” on “terrorists,” its standard term for armed rebels.

The Ministry of Information took the unusual step of issuing a statement that appeared to be aimed at countering opposition assertions of momentum.

“Media reports on the situation in Damascus are … desperate attempts intended to lift the morale of the terrorists, ” declared the official Syrian Arab News Service.