Two sets of talks on Wednesday aimed at easing tensions over Iran's nuclear program are not expected to produce any major breakthrough ahead of next month's elections in the Islamic republic.

In Vienna, the U.N. atomic agency, the IAEA, will press Iranian officials to grant access to sites, documents and scientists involved in Tehran's alleged efforts to develop atomic weapons.

Turkish riot police used water canon and tear gas on Wednesday in a bid to disperse hundreds of protesters who defied a Labor Day ban on demonstrations in a central part of Istanbul.

The ban was imposed to avoid trouble during renovation work taking place at the symbolic Taksim square, a traditional rallying point.

Expert talks between world power and Iran over Tehran's nuclear program produced no breakthrough but were positive in tone, Russia's chief negotiator on the dispute said on Thursday.

"There was certain progress. It was real but insufficient to speak of a breakthrough," Deputy Foreign Minister Sergei Ryabkov told reporters after the talks in Istanbul on Monday.

Iranian and foreign nuclear experts gathered in Istanbul on Monday to discuss Tehran's controversial atomic program, a European Union spokeswoman said.

"The meeting is taking place at the expert-level as planned," said Maja Kocijancic, spokeswoman for EU foreign policy chief Catherine Ashton, who is leading talks between Iran and the so-called P5+1 -- Britain, China, France, Russia, the United States and Germany.

Turkish police have arrested 11 people over the murder of an American woman who disappeared while visiting Istanbul last month, police and the local media reported Sunday.

The body of 33-year-old Sarai Sierra, a mother of two, was found on Saturday near Istanbul's ancient city walls with fatal head wounds, the Radikal daily reported.

Turkish Airlines said Friday a plane with 114 people aboard made an emergency landing after it was struck by lightning and one of its engines caught fire.

It said the plane, en route to Izmir from Istanbul, was preparing to land at Izmir when the lightning struck late Thursday.

Foreign Minister Adnan Mansour has said the Syrian war has "negative ramifications" for the region but advocated dialogue as the only solution to the crisis.

"There should not be any external military or any other kind of intervention," said Mansour at a one-day summit in Istanbul on Saturday.

At least on police officer died and five people were severely wounded on Tuesday in a suicide bombing that targeted a police station in central Istanbul, Turkish media reported.

The attacker came running towards the police station in the central Sultangazi neighborhood and blew himself up at the entrance, partially caving in the front door and the ceiling, said witnesses.

Forty-four people, many of them journalists, went on trial in Turkey on Monday for alleged links to outlawed Kurdish rebels, the third trial in a wave of legal action targeting the group.

The suspects are accused of links with the Union of Kurdistan Communities (KCK), an organization deemed by the authorities as the urban wing of the outlawed Kurdistan Workers' Party (PKK).

A fire that broke out at a 42-storey building in the heart of Istanbul on Tuesday was contained after a massive intervention by fire engines and emergency teams who rushed to the scene, media reported.

There were no immediate reports of deaths or injuries and the fire engulfing the exterior facade of the building was contained, the Anatolia news agency said.