A Syrian rebel targets Assad tanks with a TOW missile Screenshot/https://www.youtube.com/watch?v=JZ8T3ugKGto BEIRUT (Reuters) - The Syrian army and allied Iranian and Hezbollah forces are preparing for a ground offensive against insurgents in the Aleppo area backed by Russian air strikes, two senior regional officials familiar with the plans said on Tuesday.

The offensive would expand on a ground attack launched by the same alliance last week that is targeting rebels in Hama province further west.

The officials, speaking on condition of anonymity, said thousands of Iranian troops had arrived to take part in the ground offensives in support of President Bashar al-Assad.

A big government offensive in the area near the Turkish border is likely to further anger NATO member Ankara, which has backed insurgents fighting Assad and has already expressed deep concern over Russian air strikes that have targeted them.

Control of Aleppo city and the surrounding province is divided among the Syrian government, a range of insurgent groups fighting Assad, and the Islamic State group that controls some rural areas near the city.

"The big battle preparations in that area are clear," said one of the officials. "There is a large mobilization of the Syrian army ... elite Hezbollah fighters, and thousands of Iranians who arrived in stages in recent days," said the official.

The second official, who is close to the Syrian government, said: "The decision to launch the battle of Aleppo has been taken ... It is no longer hidden that thousands of Iranians are now in Syria and their role is fundamental."

Both officials said the attack would begin soon.

A general in the Iranian Revolutionary Guards Corps, Hossein Hamedani, was killed in Aleppo province while advising the Syrian army on their battle against Islamic State in the area, the guards said on Friday.

The city of Aleppo was Syria's most populous before the civil war began in 2011 after Assad cracked down on anti-government protests.

The government controls western areas of the city, and an array of insurgent groups control the east.

Islamic State and other insurgents, including groups backed by Assad's foreign enemies, have been fighting each other north of the city in an area of territory where Turkey and the United States have been laying plans to crush Islamic State.

The northern Aleppo region is one area where the U.S.-led coalition bombing Islamic State in Syria has flown missions.

Russia says its air strikes in Syria that began Sept. 30 were targeting Islamic State, though many of them have struck in areas held by other rebel groups, including some that have received backing from Assad's foreign enemies.

Last week, Islamic State fighters seized a number of villages near Aleppo city from other insurgent groups. Syrian state TV announced government forces had captured an area from Islamic State just north of the city on Monday.

(Writing by Tom Perry; Editing by Grant McCool)