People wave Turkey's national flags during a rally against Kurdish militant attacks on Turkish security forces, in Istanbul on Sunday.

AFP/Istanbul

More than 100,000 people - many waving Turkish flags - attended an "anti-terrorism" rally in Istanbul on Sunday, AFP reporters estimated, as President Recep Tayyip Erdogan presses a major offensive against Kurdish rebels.

The huge crowd thronged Yenikapi Square on the shores of the Marmara Sea for the demonstration, which was to culminate with an address by Erdogan.

On Thursday, thousands took part in a similar rally in the capital Ankara to denounce the Kurdistan Workers' Party (PKK), which has killed dozens of police and soldiers in a string of attacks in the mainly Kurdish southeast since the collapse of a two-year ceasefire in July.

Many of the demonstrators wore red headbands that eulogised the slain security force members as "martyrs".

"Martyrs never die, the homeland cannot be divided," the headbands read.

Erdogan's two-month-old offensive against the outlawed PKK - which comes as the country prepares for a November 1 general election - has divided Turks.

His critics accuse him of using a suicide bombing in a southeastern Turkish town that was blamed on Islamic State (IS) jihadists as a pretext for reigniting a three-decade conflict with the PKK for electoral gain.

Erdogan has tarred the PKK and IS with the same brush of extremism, but devoted much more firepower to airstrikes on PKK's bases along Turkey's border with Iraq than to air raids against the Kurds' jihadist foes.

'Terrorists in parliament'  

No political emblems were visible among the sea of red Turkish flags in Istanbul but many of the demonstrators expressed fervent support for Erdogan's Islamic-rooted Justice and Development Party (AKP).

"We will support Erdogan to the end. We are behind him because he defends our flag and our nation," Gunel Yildiz, a 43-year-old textile industry worker, who carried a giant Turkish flag, told AFP.

The AKP is looking to the upcoming election to reverse the losses it sustained in the last election in June, which stripped it of its governing majority, forcing it into coalition talks that ended in failure.

The big winner of that vote was the pro-Kurdish Peoples' Democratic Party (HDP) which took votes from the AKP to win seats in parliament for the first time.

"Believe me the terrorists won't return to parliament," Alev Akmurat, a 22-year-old student said. "The AKP will regain power, God willing," he added.

The government has accused the HDP of being a front for the PKK, allegations the party - which also enjoys support among non-Kurds - rejects.

While the timing of the offensive against the rebels has raised eyebrows in Turkey and abroad, the PKK's bloody response has caused widespread anger.

Over 120 soldiers and police have been killed in rebel attacks since the escalation began, according to pro-government media. The government for its part claims to have killed over a thousand rebels in air strikes and ground operations in northern Iraq and southeast Turkey.