Defected Syrian Prime Minister Riyad Hijab and his family crossed the border into Jordan on Wednesday morning, Information Minister Samih Maayatah said, clarifying previous reports he had done so at the weekend.

"Hijab and members of his family entered Jordan during the early hours of Wednesday," Maayatah, also government spokesman, told AFP without elaborating.

Some 2,400 people crossed into Turkey overnight to escape the escalating violence in Syria, Turkey’s government-run news agency reported on Wednesday.

The Anadolu Agency said that the crowd included 37 Syrian army officials two of whom were generals and two colonels.

Syrian tanks stormed a rebel-held district of Aleppo on Wednesday, sparking fierce clashes that a security official said marked the start of a long-threatened ground assault on the key battleground city.

The assault on the country's commercial capital came as Amnesty International raised concerns about the plight of civilians in the city and warned both sides they would be held accountable for any attacks on civilians.

The Syrian army shelled several districts of Aleppo before dawn on Wednesday, killing 12 people in the northern city while another civilian died elsewhere in the province, a monitor said.

Among the dead were a woman and her two children, killed when a shell landed on their house in al-Mashatiyah neighborhood, said the Syrian Observatory for Human Rights.

"Retired" members of Iran's Revolutionary Guards and army are among the 48 Iranians taken hostage in Syria by rebels, Iranian Foreign Minister Ali Akbar Salehi said on Wednesday, the ISNA news agency reported.

But he said those former military personnel were exclusively on a religious pilgrimage to Damascus when they were seized on Saturday.

Amnesty International expressed alarm about the plight of civilians around Aleppo, saying satellite images show intensifying use of heavy weapons near residential areas of Syria's second city.

The human rights watchdog warned the forces loyal to President Bashar al-Assad and rebels that attacks on civilians would be documented and the culprits held accountable.

Outgoing U.N.-Arab League envoy Kofi Annan will not send a representative to a meeting on the Syria conflict to be hosted by Iran on Thursday, a U.N. spokesman said.

Iran has called a ministerial meeting of states that have taken a "realistic and principled stand" on the Syrian crisis. Iran, a key ally of Syria's President Bashar Assad, has said it expects representatives from 10 countries to attend.

Jordan's King Abdullah II warned in an interview aired Tuesday that President Bashar Assad could make a "worst case scenario" retreat to an Alawite stronghold if he falls from power in Damascus.

The king peered into the mind of the embattled Syrian leader in an interview with CBS News "This Morning" and said that such an outcome to the Syria crisis could splinter the country and cause ethnic strife for decades to come.

Anti-regime gunmen killed 16 civilians, mostly Alawites and Christians, in an attack Tuesday on a housing compound for power company employees near Homs, the Syrian Observatory for Human Rights said.

"Armed men stormed the Jandar Residential Compound, firing indiscriminately and killing 16 Syrians, among them six Christians, six Alawites -- including the compound director -- and four Sunnis," said Observatory director Rami Abdel Rahman.

Syria's rebel forces attacked an oil field in the eastern province of Deir Ezzor on Tuesday, triggering a deadly firefight with troops, the Syrian Observatory for Human Rights said.

Four rebel fighters and six soldiers were killed in a fierce clash that broke out with regime forces following the attack, said the Britain-based monitoring group.