Syria yesterday admitted it has chemical weapons and warned of using them if attacked, though not against its own civilians, as regime troops reclaimed most of Damascus after a week of heavy clashes.

Any stocks of chemical weapons that may exist, will never, ever be used against the Syrian people

Fighting was still raging in Syria’s second-biggest city of Aleppo, however, as rights activists reported violence across the country killed at least 52 people, including 24 civilians.

And Russian President Vladimir Putin, the Syrian regime’s main international ally, warned of a protracted civil war should rebels be allowed to remove President Bashar al-Assad from power.

At a Damascus news conference, foreign ministry spokesman Jihad Makdissi warned Syria would use chemical weapons if attacked by outsiders, although he backtracked later to say that, if Damascus has them, they would be secured.

His remarks come amid growing international concern that Damascus is preparing to deploy its chemical arsenal in the repression of a 16-month uprising against the Assad regime.

“Syria will not use any chemical or other unconventional weapons against its civilians, and will only use them in case of external aggression,” Mr Makdissi told reporters.

“Any stocks of chemical weapons that may exist, will never, ever be used against the Syrian people,” he said, adding that in the event of foreign attack, “the generals will be deciding when and how we use them”.

Mr Makdissi stressed later in an e-mail that Syria would “never use chemical and biological weapons during the crisis... and that such weapons, if they exist, it is natural for them to be stored and secured.”

The US warned Syria over the use of chemical arms. “They should not think one iota about using chemical weapons,” Pentagon press secretary George Little told reporters.

The White House has said Washington would “hold accountable” any Syrian official involved in the release or use of the country’s chemical weapons.

UN chief Ban Ki-moon said the use of chemical arms would be “reprehensible” and stressed “all the countries have an obligation not to use any weapons of mass destruction, whether they are parties or not to any convention or agreement”.

Mr Ban also announced that UN peacekeeping chief Herve Ladsous as well as chief UN military adviser General Babacar Gaye were travelling to Syria yesterday.

General Gaye is due to take over the command of the UN Supervision Mission in Syria (UNSMIS) which was extended with a “final” 30-day mandate last week by the Security Council.

On the political front, Mr Makdissi said Syria firmly rejected a demand by the Arab League that Mr Assad step down.

“We are sorry that the Arab League has descended to this level concerning a member state of this institution,” he said. “This decision only concerns the Syrian people, who are the sole masters of the fate of their governments.”

The Arab League had called late on Sunday on Mr Assad to “renounce power”, promising he and his family would be offered “a safe exit”.

Mr Putin warned of a protracted civil war in Syria should rebels be allowed to remove Mr Assad from power.

“We are afraid that if the country’s current leadership is removed from power unconstitutionally, then the opposition and today’s leadership may simply change places,” Interfax news agency quoted Putin as saying.

In that case “a civil war will stretch on for who knows how long,” the Russian leader warned.

Iraq also rejected the Arab League call for Mr Assad to step aside, describing it as interference.

Prime Minister Nuri al-Maliki, meanwhile, instructed Iraqi forces and the Red Crescent to allow in Syrian refugees and provide them with support, reversing an earlier decision.

Tens of thousands of Syrians have fled for neighbouring countries in recent days after violence mounted, particularly in Damascus.

On the ground, government forces reclaimed most of Damascus, after a week of heavy fighting with rebels, who remain in the city but are planning a guerilla strategy, activists and regime sources said.

A security source in Damascus confirmed the city had been reclaimed by government forces. Elsewhere, rebels and troops clashed violently in Syria’s commercial hub Aleppo, where the rebel Free Syrian Army says a war of “liberation” is also underway.

Clashes engulfed the eastern Sakhur and Hanano City districts, leading residents to flee, according to the Syrian Observatory for Human Rights.

The regime also used helicopters to pound the central city of Homs –symbol of the uprising – and nearby rebel-held Rastan, activists said.

The Britain-based Observatory says more than 19,000 people have been killed since the uprising began in March 2011.

The EU yesterday beefed up sanctions against Mr Assad’s regime and agreed to tighten an arms embargo by inspecting vessels and planes suspected of carrying arms, diplomats said. In fact EU foreign ministers began talks in Brussels with an agreement to freeze the assets of 26 Syrians and three firms close to the Assad regime in the 17th round of sanctions since anti-regime protests erupted last year, they said.

EU officials said the bloc was ready to evacuate its nationals from Syria via Cyprus if necessary. “We are prepared for the worst,” said Cypriot Home Affairs Minister Eleni Mavrou, whose country currently holds the EU helm.

A chronology of latest developments in conflict

• The Syrian Observatory for Human Rights says regime forces “summarily executed” at least 23 people in the Damascus neighbourhoods of Mazzeh and Barzeh the previous day. The bodies of some showed signs of torture, it says.

• Fifteen unidentified bodies were also found in Maadamiyat al-Sham village near Damascus, the watchdog says. Some of them had their hands tied, while others showed signs of having been stabbed.

• Troop reinforcements are deployed in areas of Damascus and conducted raids after night-time clashes in the capital. They carried out raids in Mazzeh, as well as Nahr Aysha, and Lawan in Kfar Sousa, according to the Observatory, which reports more than 50 killed across the country yesterday.

• Activists and government sources said regime forces reclaimed most of Damascus after a week of heavy fighting with rebels, who are using guerilla tactics to keep a foothold in the capital. The head of the Observatory, Rami Abdel Rahman, said “regime troops have taken control of some areas, but in others the rebels are still present”.

• Activists reported fierce clashes between rebels and troops in the northern city of Aleppo. Troops also use helicopters to pound the central city of Homs − symbol of the uprising − and nearby rebel-held Rastan.

• The regime admitted it possesses chemical weapons and warned it would use them if attacked though not against its own civilians.

• The US warned Syria not to even consider using chemical weapons. UN chief Ban Ki-Moon said the use of chemical weapons in Syria would be “reprehensible”.

• The West boosted humanitarian aid to Syrian refugees. The EU also beefed up its sanctions and agreed to tighten an arms embargo against Syria.

• The opposition Syrian National Council called on rebels to redouble their efforts, saying “the regime is wobbling, but it will not surrender easily”.

• Prime Minister Nuri al-Maliki instructs Iraq’s security forces and Red Crescent to allow in Syrian refugees and provide them with support, reversing an earlier decision. Clashes take place between Syrian refugees and Jordanians in the border town of Ramtha.

• Russian President Vladimir Putin warned of a protracted civil war if Mr Assad be “unconstitutionally” removed from power by rebel fighters.