ANKARA (REUTERS, AFP) - At least 95 people were killed in Ankara Saturday when bombs set off by two suspected suicide attackers ripped through a crowd of leftist and pro-Kurdish activists at an anti-government peace rally, in the deadliest attack in the history of modern Turkey.

The twin blasts, near Ankara's main train station, ratcheted up tensions ahead of Turkey's Nov 1 snap elections which were already soaring amid the government's offensive on Kurdish militants.

Bodies of slain demonstrators were seen strewn across the ground after the explosions, with the banners they had been holding for the "Work, Peace and Democracy" rally lying next to them..

The attack also left 246 wounded, 48 of whom are in intensive care, according to an updated toll announced by Prime Minister Ahmet Davutoglu's office.

President Recep Tayyip Erdogan denounced the "heinous attack", saying it was aimed at "our unity and our country's peace."

Declaring three days of mourning, Davutoglu said there were "strong signs" the attack were carried out by two suicide bombers.

Interior Minister Selami Altinok said he would not resign, denying there was a "security vacuum" in policing at the rally.

There were scenes of chaos after the blasts, as ambulances raced to get to the wounded and police cordoned off the blood-stained area around the train station.

"We heard one huge blast and then one smaller explosion and then there was a great movement and panic. Then we saw corpses around the station," said Ahmet Onen, 52.

"A demonstration that was to promote peace has turned into a massacre, I don't understand this," he said, sobbing.

Turkish police fired into the air to disperse demonstrators angered by the deaths of their fellow activists, an AFP correspondent at the scene reported.

'BARBARIC ATTACK'

Davutoglu said no one had claimed responsibility for the bombings but that groups including the Islamic State in Iraq and Syria (ISIS) extremists, the Kurdistan Workers' Party (PKK) and the far-left Revolutionary People's Liberation Party-Front (DHKP-C) were capable of carrying out such an attack.

Amateur footage filmed moments before the blasts and broadcast by NTV television showed smiling activists holding hands and dancing before suddenly falling to the ground as a huge explosion went off behind them.

Reports said hundreds of people in Ankara rushed to hospitals to donate blood for the victims.

The death toll surpassed that of the May 2013 twin bombings in Reyhanli on the Syrian border that killed over 50 people.

With international concern growing over instability in the key Nato member, EU foreign policy chief Federica Mogherini urged Turkey to "stand united against terrorists."

UN Secretary-General Ban Ki-moon said in a statement he "expects the perpetrators of these terrorist acts to be swiftly brought to justice".

French President Francois Hollande condemned the "odious terrorist attack", while Russian President Vladimir Putin passed his condolences to Erdogan.

US National Security Council spokesman Ned Price said "the fact that this attack occurred ahead of a planned rally for peace underscores the depravity of those behind it."

Turkey's pro-Kurdish Peoples' Democratic Party (HDP) had been one of the groups that called for the peace rally.

"We are faced with a huge massacre. A barbaric attack has been committed," said HDP leader Selahattin Demirtas, blaming a "mafia state" and a "state mentality which acts like a serial killer" for the attack.

Among those killed was Kubra Meltem Mollaoglu, an HDP member who was standing for parliament in the upcoming polls.

PKK SUSPENDS ACTIVITIES

In Istanbul, some 10,000 people marched down the city's main central avenue later on Saturday to denounce the attacks.

Thousands also took to the streets in solidarity in Paris, Strasbourg and Marseille in France, as well as in Zurich in Switzerland.

The attack comes with Turkey on edge ahead of the Nov 1 polls following a wave of unrest over the past few months.

An attack in the predominantly Kurdish town of Suruc on July 20 targeting pro-HDP activists and blamed on ISIS killed 32 people.

The PKK accused Ankara of collaborating with the militants and resumed attacks on the security forces after observing a two-year ceasefire.

Over 140 members of the security forces have since been killed while Ankara claims to have killed more than 1,700 Kurdish militants in weeks of bombardments of PKK targets in south-east Turkey and northern Iraq.

The PKK on Saturday announced it would suspend all attacks - except in self defence - ahead of the polls.

"Heeding calls from Turkey and abroad, our movement has decided on a state of inactivity by our guerrillas, unless our people and our guerilla forces are attacked," the Kurdistan Communities Union (KCK), an umbrella movement that includes the PKK, said in a statement.

The HDP performed strongly in the last election on June 7, winning 80 seats in parliament to deprive Erdogan's ruling Justice and Development Party (AKP) of an outright majority for the first time since it came to power in 2002.

The AKP then failed to form a coalition in months of talks, prompting Erdogan - who had been hoping for a large majority to push through reforms to boost his powers - to call another election on Nov 1.

Many Twitter users in Turkey, meanwhile, were unable to access the social media network Saturday.

It was not immediately clear if the problem was related to the attack, but the Turkish government has moved before to block or limit social media sites - including Twitter - at sensitive times, prompting accusations of censorship.

No Singaporeans affected: MFA

The Singapore Embassy in Ankara has verified that there were no Singaporeans affected by the explosions.

In response to media queries on the explosions in Ankara, Turkey on Saturday, a Ministry of Foreign Affairs (MFA) spokesman said: "Singapore condemns the bomb blasts in Ankara and is saddened by the loss of innocent lives. We convey our condolences to the families of the victims, and wish the injured a speedy recovery.