The suspected arsonist behind a deadly fire at a Brussels mosque said Tuesday he set the Shiite place of worship ablaze to scare the community he blames for the violence in Syria, officials said.

Belgium's Muslim community was in shock a day after the attack that left an imam dead.

At least 48 persons were reported killed in violence across Syria on Tuesday, including 25 members of the security forces, as a pro-government daily said the regime had captured the rebel city of Idlib.

"Twelve members of the security services who headed for the town of Dael to carry out arrests were killed ... when their vehicle was ambushed by a group of armed deserters," said the Syrian Observatory for Human Rights.

CIA chief David Petraeus met Turkey's Prime Minister Recep Tayyip Erdogan on Tuesday for closed-door talks focusing on the crisis across the border in Syria.

Petraeus, director of the U.S. Central Intelligence Agency, also discussed the latest developments in neighboring Iran and efforts to counter Kurdish rebels attacking Turkey from safe havens in northern Iraq, said NTV television channel.

U.S. Secretary of State Hillary Clinton on Tuesday vowed to press ahead with support for democracy promotion groups, saying that they play a critical role despite a crackdown in Egypt.

Clinton, addressing U.S. ambassadors from around the world who are back in Washington for a group conference, said that civil society groups are vital to encouraging U.S. goals such as advancing democracy and women's participation.

Arab League chief Nabil al-Arabi on Tuesday called for an international probe into "crimes" committed against civilians in Syria, particularly in the flashpoint provinces of Homs and Idlib.

"Media reports about the horrible pictures concerning crimes committed against innocent civilians in Homs and Idlib and other parts of Syria can be described as crimes against humanity," Arabi said in a statement.

The U.N. human rights office will send observers to Syria's neighboring countries to collect evidence and document atrocities in the strife-torn state, the deputy rights commissioner said Tuesday.

"We will be sending monitors for information collection and documentation of the violations and atrocities in the border areas in the neighboring countries later this week," said Kang Kyung-wha, Deputy High Commissioner for Human Rights.

Syria's embattled President Bashar al-Assad issued a decree on Tuesday setting May 7 as the date for parliamentary elections that were delayed last year, the state news agency SANA reported.

The vote is part of a raft of reforms announced by Assad in a bid to calm a year-long uprising against his regime that began with democracy protests.

Baghdad's international airport will shut from March 26 until the end of an Arab League summit in the Iraqi capital on March 29, the country's civil aviation chief told Agence France Presse on Tuesday.

"We will close off flights from the 26th until the end of the summit," said Nasser Hussein Bandar, head of Iraq's civil aviation authority. "It (the airport) will be used for receiving delegations."

Russia said Tuesday it will press Syria to accept international monitors who could observe the implementation of a "simultaneous" ceasefire between government troops and rebels.

Foreign Minister Sergei Lavrov said Russia was discussing the proposal with both the Arab League countries and at the United Nations, where the Security Council debated the crisis on Monday.

Syria has planted landmines near its borders with Lebanon and Turkey, along routes used by refugees fleeing the strife-torn country, Human Rights Watch (HRW) charged on Tuesday.

"The Syrian regime is trying to prevent people from going in and from fleeing the country," said Nadim Houry, deputy director of the group's Middle East and North Africa division.