Updated

The Latest on Syria talks in Iran (all times local):

1:25 p.m.

Activists and residents say warplanes have struck areas on the southern edge of the Syrian Idlib province, the rebels' last bastion, killing one and causing loud explosions and large plumes of smoke.

The airstrikes Friday come hours before presidents of Iran, Russia and Turkey meet in Tehran to discuss the war in Syria, with all eyes on a possible military offensive to retake bastion of Idlib.

Rami Abdurrahman, the head of the Britain-based Syrian Observatory for Human Rights, said a series of airstrikes struck a few villages in southwest Idlib and along the borders with the adjacent Hama province, targeting insurgent posts and killing a fighter. Abdurrahman said suspected Russian warplanes carried out the airstrikes.

Idlib province and surrounding areas are home to more than 3 million people.

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12:55 p.m.

The spokesman for Iran's Foreign Ministry is calling a summit on Syria between Iran, Turkey and Russia an "invaluable opportunity."

Bahram Ghasemi wrote an opinion piece published across Iranian media on Friday that the summit in Tehran helps as all the nations "have faced similar challenges and joint threats by bullying foreign powers."

Ghasemi wrote: "The summit has double significance since all the three nations have faced ambitions and greediness of an illogical international big power." That refers to the United States, which has some 2,000 troops in Syria after its war against the Islamic State group.

The summit Friday between Iranian President Hassan Rouhani, Russian President Vladimir Putin and Turkish President Recep Tayyip Erdogan may determine whether diplomacy halts any military action ahead of an anticipated offensive targeting Syria's northwestern Idlib province.

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9:55 a.m.

The presidents of Iran, Russia and Turkey will meet in Tehran to discuss the war in Syria, with all eyes on a possible military offensive to retake the last rebel-held bastion of Idlib.

The summit Friday, the third between Iranian President Hassan Rouhani, Russian President Vladimir Putin and Turkish President Recep Tayyip Erdogan, may determine whether diplomacy halts any military action.

Northwestern Idlib province and surrounding areas are home to about 3 million people — nearly half of them civilians displaced from other parts of Syria. That also includes an estimated 10,000 hard-core fighters, including al-Qaida-linked militants.

Iran, Russia and Turkey all have their own competing interests over Syria. All also face U.S. sanctions under the administration of President Donald Trump.