- NEW: Another 1,316 civilians and 12 soldiers defect to Turkey, a Turkish official says
- NEW: Iran's foreign minister will meet Turkish officials about Syria on Tuesday
- At least 11 people are killed across Syria on Tuesday, opposition activists say
- Opposition: Aleppo, the country's cultural and commercial hub, comes under fierce shelling
Aleppo, Syria (CNN) -- Reports of bloodshed in Syria's largest city continued unabated Tuesday as an activist group said it had photographic evidence of heavy weapons used near residential parts of the Aleppo area.
Fierce artillery shelling fell on several Aleppo neighborhoods Tuesday morning "amid a state of panic among residents," opposition activists said.
"Many people" were injured in the Shaar neighborhood, which is suffering a humanitarian crisis amid a lack of doctors and medical supplies, the opposition Local Coordination Committees of Syria said.
CNN's Ben Wedeman in Aleppo described a dire situation in which men, women and children waited 1 1/2 hours to receive free bread from the rebel Free Syrian Army. Many started to pack up and leave.
At least 11 people were killed across Syria early Tuesday, the LCC said.
Amnesty International released a series of satellite images from the Aleppo area, including one that shows "more than 600 probable artillery impact craters" in the nearby town of Anadan.
"Turning Syria's most populous city into a battlefield will have devastating consequences for civilians. The atrocities in Syria are mounting already," said Christoph Koettl, emergency response manager for Amnesty International USA. "The Syrian military and the opposition fighters must both adhere to international humanitarian law, which strictly forbids the use of tactics and weapons that fail to distinguish between military and civilian targets."
The incessant violence in Syria spurred another 1,316 civilians and 12 soldiers to flee to Turkey on Monday night, Turkish Foreign Ministry spokesman Selcuk Unal said Tuesday. The soldiers included one brigadier general, Unal said on Twitter.
"With the latest arrivals, the number of our Syrian guests living in the shelter centers in our country reached close to 47,500," Unal said. "These numbers and the numbers of Syrians in other countries show how grave the situation in Syria is."
Iranian Foreign Minister Ali Akbar Salehi is expected to visit Turkey on Tuesday, Unal said, with Syria on the list of regional issues to be discussed.
"The steps that the Syrian regime needs to take were and are clear. The Syrian administration has to first stop firing on its own people," Unal said, adding that "Turkey is not sending armed elements to its neighbors."
Iran, which has defended the Syrian regime, will likely have a different take on the Syrian civil war.
Iranian parliament speaker Ali Larijani blamed the United States and other countries for the deaths of Iranian pilgrims in Syria, the semi-official Iranian Students News Agency reported.
Syrian State-run media reported over the weekend that "armed terrorists" had attacked and kidnapped 48 Iranian Shiite pilgrims on a bus near the capital. Three Iranian prisoners were killed in the Damascus suburbs during heavy shelling Monday, according to the LCC
Meanwhile, former Prime Minister Riyad Hijab was out of the country Tuesday, a day after defecting from President Bashar al-Assad's regime.
"I announce today my defection from the killing and terrorist regime, and I announce that I have joined the ranks of the freedom and dignity revolution. I announce that I am from today a soldier in this blessed revolution," Hijab said in a written statement, read by a Syrian opposition official Monday on Al Jazeera.
Al-Assad appointed Hijab as prime minister about 2 months ago -- roughly the same time when Hijab started hatching his plan to defect, said Hijab's spokesman, Muhammad el-Etri said.
The former prime minister escaped Syria with the help of the rebel Free Syrian Army, el-Etri said.
Hijab's defection drew optimism from officials in Washington.
"The momentum is with the opposition and with the Syrian people. It is clear that these defections are reaching the highest levels of the Syrian government, and Assad cannot restore his control over the country because the Syrian people will not allow it," White House spokesman Jay Carney said.
But some analysts said Hijab's departure doesn't necessarily mean al-Assad's regime will implode anytime soon.
"The prime minister in Syria is the head of the government, but the government in Syria doesn't rule the country," said Andrew Tabler of the Washington Institute for Near East Policy. "It's the regime, and the regime includes the security services, the army and the members of the Assad family."
In addition, al-Assad's regime is comprised primarily of minority Alawites, while Hijab is a Sunni.
"The lack of any meaningful leadership defections from the Alawite sector of the regime is very distressing," said Aram Nerguizian of the Center for Strategic and International Studies. Sunni defections have not weakened the regime's inner core, he said.
Nonetheless, Hijab's departure is considered the highest-profile defection from the Syrian government.
In July, one of Syria's most senior diplomats -- Nawaf al-Fares -- defected, publicly embraced his country's uprising and called for a foreign military intervention. Al-Fares was Syria's ambassador to Iraq.
Manaf Tlas, a Sunni general in Syria's elite Republican Guards, also defected last month.
It was not clear exactly where Hijab was on Tuesday.
El-Etri, his spokesman, said Monday that Hijab was "in a country neighboring Syria" and would be heading to Qatar "sometime soon."
George Sabra, a spokesman for the opposition Syrian National Council, said Monday that Hijab arrived with his family in Jordan.
Roughly 17,000 people have been killed since the Syrian conflict first flared in March 2011, when government forces began cracking down on protesters, U.N. Secretary-General Ban Ki-moon said last month. The opposition put the toll at more than 20,000.
Complete coverage: Unrest in Syria
CNN's Jomana Karadsheh, Yesim Comert, Salma Abdelaziz, Holly Yan, Jill Dougherty and Jamie Crawford contributed to this report.
