Syrians flee as battle blazes across Damascus and Aleppo An image grab taken from a video uploaded on YouTube shows smoke billowing from a neighbourhood of Damascus. Syria was in the grip of bloody urban warfare on Sunday, with fierce fighting between the Free Syrian Army and government forces raging on the streets of Damascus and in the northern city of Aleppo. The Syrian army bombarded several districts of the capital using helicopter gunships, video footage showed. Smoke could be seen pluming across the city. Tanks and soldiers besieged the northern Barzeh district, previously a centre of rebel resistance, with the army carrying out what it called mopping up operations in Marzeh, another opposition enclave. Many shops were shut. Only a few central areas were unaffected, with Damascus resembling a war zone. There was also fighting in Aleppo, Syria's historic biggest city. The Free Syrian Army, which penetrated into Aleppo late last week, was battling Syrian troops equipped with gunships and tanks. The rebels were in control of several areas of the city, with fighting around the intelligence headquarters. There were clashes in other parts of the country too, including the eastern city of Deir al Zor on the Euphrates and in Homs. Syria's brutal 16-month conflict now appears to be moving from the countryside into the cities, with rebels increasingly adept at staging guerrilla-style attacks followed by tactical withdrawals. Activists on Sunday said the death toll had gone up sharply to more than 19,000. The UK-based Syrian Observatory for Human Rights said July was shaping up to be the deadliest month of the conflict so far, with 2,752 people killed in the first three weeks. More than 30,000 Syrians have fled to neighbouring Lebanon, with others still seeking to escape. The Syrian government insisted the situation inside the capital on Sunday was normal. It released photographs of President Bashar al-Assad meeting his new chief of staff, General Ali Abdullah Ayyoub. The photograph was impossible to authenticate, although the Israeli military said Assad and his family were still in Damascus. Soldiers were dealing with a few remaining "terrorists," state television said. However, the deteriorating situation led Israel's prime minister, Binyamin Netanyahu, to warn that his country would "have to act" if the Syrian regime collapsed and there was a risk its chemical weapons and missiles could fall into the hands of militant groups. In an interview on Fox News Sunday, Netanyahu said Israel had not considered specifically trying to cross the border to seize the weapons but added: "There are other possibilities." He said preventing Syria's weapons from falling into the wrong hands was key to Israeli security. Could you imagine Hezbollah, the people who are conducting with Iran all these terror attacks around the world - could you imagine them having chemical weapons? It would be like al-Qaida having chemical weapons," he said. It's something that is not acceptable to us, not acceptable to the United States and to any peaceable country in the world. So I think that this is something we'll have to act to stop if the need arises. And the need might arise if there's a regime collapse, but not a regime change," he said. The battle for Damascus follows a devastating bomb attack last Wednesday at the national security headquarters which killed four members of the president's top military and security command. The circumstances of the attack remain unclear. On Sunday, rebels said they had captured a third border crossing with Turkey at Bab al-Salam, north of Aleppo, and close to the Turkish town of Antakya, already overflowing with Syrian refugees. "The Free Syrian Army has taken control of the Bab al-Salam crossing, but Assad's forces are bombarding our positions from afar," Ahmed Zaidan, spokesman for an opposition group called the Higher Council of the Revolution's Leadership, told Reuters. Video showed triumphant rebels posing at the border with the pre-Ba'athist revolutionary flag. Iraqi officials said the Syrian army had used a helicopter gunship and recaptured one of two remote border crossings with Iraq briefly seized by the opposition. Colonel Abdul-Jabbar Mohammed Aqidi, the commander of rebel forces in Aleppo province, said: "We gave the orders for the march into Aleppo with the aim of liberating it." He said in a video: "We urge the residents of Aleppo to stay in their homes until the city is liberated." He added that rebels were fighting inside the city while others were moving in from the outskirts. Aqidi called on government troops to defect and join the opposition, and claimed rebels would protect members of the minority Alawite sect, the offshoot of Shia Islam to which Assad belongs, saying: "Our war is not with you but with the Assad family." An Aleppo-based activist, Mohammed Saeed, told Reuters the fighting was concentrated in several neighbourhoods. Saeed said rebels were in full control of the central Salaheddine district and the nearby Sakhour area. He added that thousands of residents had fled tense quarters of the city for safer neighbourhoods and the suburbs. "Aleppo is witnessing serious street battles" and many shops are closed, Saeed said. He said there were fierce clashes on the road leading to the city's international airport, as rebels tried to surround the airfield to prevent the regime from sending reinforcements. Despite the regime's unflagging efforts to present an image of calm in the capital, Malaysia's government said it was shuttering its embassy in Damascus and evacuating more than 130 students and diplomats, while Italy ordered of its citizens to leave the country because of the "progressive deterioration" of the situation.