The Syrian army shelled the Salaheddin district of Aleppo on Saturday in its push to drive out rebels, as gunfire and bomb blasts rang out across Damascus, monitors and state media said.

State television said two bombs exploded in the heart of the capital, without reporting casualties.

The renewed violence came as at least 21 people were killed in violence across Syria, according to the Syrian Observatory for Human Rights.

The Britain-based monitoring group said “areas of (southwest) Salaheddin district came under shelling by Syrian regime forces,” who forced the rebels to stage what they termed a “tactical withdrawal” from the area on Thursday.

A rebel commander insisted his fighters were still putting up strong resistance around Salaheddin.

“Fierce fighting has continued without respite for the past 24 hours as the army tries to push us out of the neighbourhood,” Abdel Qader Saleh told AFP by telephone.

Troops backed by artillery stormed Salaheddin on Wednesday in the first stage of an offensive to recapture areas of the city taken by the rebels since July 20.

Regime forces on Saturday also shelled the eastern Aleppo district of Saif al-Dawla, the western neighbourhoods of Bustan al-Qasr and Al-Masharaqa, and Malak district, where one rebel was killed, the Observatory said.

In Damascus, witnesses reported gunfire on the densely-populated Baghdad Street in the heart of the capital.

Elsewhere in central Damascus, state television quoted an official as saying that an “armed terrorist group detonated a bomb in the Marjeh district and fired randomly.”

Fighting was also reported elsewhere in Damascus, including Tadamun, where there were “fierce clashes between the Free Syrian Army and the regime forces,” said the Local Coordination Committees, which has activists on the ground.

The Syrian Revolution General Council, another activist network, reported clashes between regime forces and FSA fighters on the Damascus-Daraa highway in the capital’s Qadam district.

The Observatory also said “shooting and explosions were heard in the Qaboon neighbourhood in Damascus,” a week after the army said the entire capital was back under its control.