BEIRUT, (Reuters) – Syria denied reports on Saturday that President Bashar al-Assad’s deputy had defected and its forces pursued an offensive against rebels, bombarding parts of Aleppo in the north and attacking an insurgent-held town in the oil-producing east.

Vice-President Farouq al-Shara “never thought for a moment about leaving the country”, said a statement from his office broadcast on state television in response to reports that the veteran Baath Party loyalist had tried to defect to Jordan.

Assad, battling a 17-month-old rebellion led by Syria’s Sunni Muslim majority that has escalated into civil war, has suffered a string of defections including by his prime minister Riyadh Hijab two weeks ago.

Shara, whose cousin – an intelligence officer – announced his own defection on Thursday, is a Sunni Muslim from Deraa province where the revolt began against Assad, a member of the minority Alawite sect that is an offshoot of Shi’ite Islam.

The 73-year-old former foreign minister kept a low profile as the rebellion mushroomed but appeared in public last month at a state funeral for three of Assad’s top security officials killed in a bomb attack in Damascus.

The statement said he had worked since the start of the uprising to find a peaceful, political solution and welcomed the appointment of Algerian diplomat Lakhdar Brahimi as a new international mediator for Syria.

Brahimi, who hesitated for days before accepting a job that France’s U.N. envoy Gerard Araud called an “impossible mission”, will replace former U.N. Secretary-General Kofi Annan, who is leaving at the end of the month in frustration over jostling among world powers that undermined his peace mandate.

Annan’s six-point plan to stop the violence and advance towards political negotiations was based on an April ceasefire agreement which never took hold. The conflict has deepened since then with both sides stepping up attacks.

Assad’s forces have resorted increasingly to air power to hold back lightly armed insurgents in the capital Damascus and Aleppo, a northern commercial hub. More than 18,000 people have died in the bloodshed and about 170,000 have fled the country, according to the United Nations.

The Syrian Observatory for Human Rights said the army bombarded neighbourhoods in Aleppo, Syria’s largest city. Rebels hold several districts in the country’s northern commercial hub and have tried to push back an army counter-offensive.

State television said soldiers “cleared terrorists and mercenaries” – terms used by authorities to describe Assad’s armed opponents – from the western district of Saif al-Dawla, where some of the heaviest fighting has taken place.

Internet footage which activists said was filmed in Saif al-Dawla on Saturday showed a plane making a low pass over buildings and dropping two bombs.

“They were defeated (in Damascus). They will be defeated very soon in Aleppo,” Deputy Foreign Minister Faisal Mekdad told Sky News in Damascus. Mekdad also denied the “absolutely scandalous” reports of Shara’s defection.

The White House said it had seen reports of Shara’s defection but could not confirm them.

“At this point, whether or not those reports are true, we have seen in the last several weeks the increasing isolation of the Assad regime,” White House spokesman Josh Earnest said to reporters travelling with U.S. President Barack Obama on Air Force One. Brahimi had Washington’s support, he added.

The Observatory also said at least 20 armoured vehicles moved into the eastern town of Mayadeen in Deir al-Zor province, where Syria’s 200,000 barrels per day of oil are produced.

More than 130 people were killed in Syria on Saturday, it said, including 15 in Deir al-Zor.

In the town of Tel, north of Damascus, local activists said the bodies of 40 people killed by bombardment were gathered together for a joint burial. A picture showed what appeared to be several corpses wrapped in colourful blankets on a street.

BRAHIMI WARNS ON U.N. SUPPORT FOR MISSION

Brahimi will have a new title, Joint Special Representative for Syria. Diplomats said this was to distance him from Annan, who complained that his peaceful transition plan was crippled by divisions between Western powers – who want Assad out – and Russia, his most important ally – in the U.N. Security Council.

Describing the situation in Syria as “absolutely terrible”, Brahimi told Reuters he urgently needed to clarify what support the United Nations can give him and said it was too soon to say whether Assad should step down – in contrast to Annan who said it was clear the Syrian leader “must leave office”.

“It’s much too early for me to say. I don’t know enough about what is happening,” Brahimi said. He had not yet held any talks with Assad but said he would meet him and the country’s opposition leaders as soon as the time was right.

Syrian opposition figure Haitham al-Maleh said Brahimi had no more chance of success than Annan’s doomed mission.

“The same way the Syrian regime caused the Arab monitors mission, international monitors delegation and Kofi Annan’s initiative to fail, they will cause the failure of Lakhdar Brahimi,” he said at the inauguration of the Cairo headquarters of the Council for the Syrian Revolution.

The last U.N. observers who deployed in Syria four months ago to monitor Annan’s failed ceasefire will leave after midnight on Sunday, when their mandate expires.

They will leave a “liaison office” open in Damascus after their departure, though its size and role have not been finalised, a U.N. spokeswoman said.

The head of the departing U.N. Supervision Mission in Syria, General Babacar Gaye, criticised both government forces and rebels for failing to meet obligations to protect civilians.

“The comfort for me is that the United Nations will stay in the country,” he told reporters in Damascus. “The United Nations is committed to ending violence, committed to triggering dialogue between the parties.”

Humanitarian conditions in Syria have deteriorated as fighting worsens, cutting off civilians from food supplies, health care and other assistance, U.N. agencies say. Sewage-contaminated water has led to a diarrhoea outbreak in the countryside around Damascus, with 103 suspected cases.