* Important to decrease violence, Brahimi says
* Heavy street clashes reported in Aleppo
* Turkey, Iran both back ceasefire
By Marwan Makdessi
DAMASCUS, Oct 19 (Reuters) - Mediator Lakhdar Brahimi will meet Syrian officials over the next few days in an effort to secure a brief ceasefire in the worsening war between President Bashar al-Assad's government and rebel forces.
Brahimi, who arrived in the capital Damascus on Friday afternoon, will meet Foreign Minister Walid al-Moualem on Saturday morning, the U.N. spokesman in Damascus, Khaled al-Masri, said. He did not say whether the envoy would meet Assad.
"We will talk about the ceasefire and the Syrian issue in general. It is important to decrease the violence - we will talk with the government and political parties and civil society about the Syrian issue," Brahimi told reporters upon arrival.
The violence showed no sign of abating, with opposition activists reporting heavy street clashes in Aleppo, Syria's biggest city, and intensified army bombing of towns along the strategic north-south highway.
In Lebanon, a huge car bomb that exploded in central Beirut during rush hour on Friday killed a top security official and seven others, wounded about 80 and heightened fears that Syria's war is aggravating tensions in its neighbour.
Brahimi, envoy for the United Nations and the Arab League, has been crisscrossing the region with the aim of convincing Assad's main backers and his foes to support a truce during the Islamic festival of Eid al-Adha next week.
U.N. Secretary-General Ban Ki-moon and Arab League chief Nabil Elaraby backed a ceasefire. "The longer the violence lasts, the more difficult it will be to find a political solution and rebuild Syria," they said in a joint statement.
Turkish Foreign Minister Ahmet Davutoglu called for all sides to observe the three- or four-day ceasefire.
"It is important that the Syrian regime, which bombards its own people with fighter planes and helicopters, halts these attacks immediately and unconditionally," Davutoglu said in Ankara.
Iran also backed the ceasefire call but added that the main problem in Syria was foreign interference - a reference to support for the rebels by Gulf Arab states, the United Sates and other Western powers, and Turkey.
"We consider the establishment of an immediate ceasefire an important step in helping the Syrian people," Iranian Deputy Foreign Minister Hossein Amir Abdullahian said, as quoted by Mehr news agency.
"Syria has taken important steps against terrorism and foreign interference and is pursuing political reforms and the security of the country."
Despite supportive words from backers of the warring factions, the task of securing even a temporary ceasefire is daunting in an intensifying conflict in which more than 30,000 people have been killed over 19 months.
PREVOUS CEASEFIRE COLLAPSED
A previous ceasefire in April collapsed after just a few days, with each side blaming the other. Mediator Kofi Annan resigned his post in frustration a few months later. Next week's truce would be self-imposed, with no international observers.
Lebanese political scientist Hilal Khashan said Turkey and Iran were probably promoting the ceasefire because "they need to seem like they are doing something".
"I don't think it will work. Neither side trusts the other, and the opposition fears the regime will use the ceasefire to bolster its positions in Aleppo and Idlib," he told Reuters in Beirut.
A rebel group calling itself the Joint Command for Military and Revolution Councils in Syria said in a video statement that it was willing to respect the ceasefire on condition that the Assad government released detainees, particularly women, and lifted the siege of the central city of Homs.
It also called for a halt in air strikes and for access to humanitarian aid - something Assad has denied to several international organisations. It also said the army must not take advantage of the truce to fortify its positions.
Other rebel groups say a decision has not yet been taken.
The war pitting Assad's troops against the loosely organised rebel army trying to end his 12 years in power has intensified in recent months.
On Thursday, 240 people were killed across the country in fighting and bombardments, from Damascus to Aleppo, the country's commercial centre.
Activists said that on Thursday planes had bombed apartment buildings and a mosque in the town of Maarat al-Numan, in the northern province of Idlib, which straddles the north-south highway, connecting the capital to Aleppo.
Video posted on YouTube showed men pulling the body parts of children from a mass of concrete that they said was a collapsed building in Maarat al-Numan.
Rebels captured Maarat last week and the government is trying retake it and restore the link to Aleppo.
The Syrian Observatory for Human Rights, a British-based opposition group that has a network of informants in Syria, said bombings continued into Friday in the same area.
In Paris, the French Foreign Ministry condemned the bombings of Maarat al-Numan which it said had killed at least 47 people, including 23 children.
"These raids against the civilian population show the horror and cruelty of the regime's implacable crackdown," spokesman Philippe Lalliot said.
"These crimes show the urgency to put in place a lasting ceasefire and a political transition that meets the aspirations of the Syrian people."
Lalliot said Brahimi's efforts to achieve a ceasefire were commendable but that while both sides had to abide by it, the attacks on Maarat al-Numan showed the conditions were not in place.