Dozens of former Turkish public officials, including former police chiefs, went on trial Tuesday on charges of negligence over the murder of Turkish-Armenian journalist Hrant Dink in 2007 that sent shockwaves around the country.

The suspects face accusations of failing to uncover the plot to murder Dink, the editor-in-chief of the Turkish-Armenian bilingual weekly Agos and a passionate advocate of reconciliation between Turks and Armenians.

More rockets hit a Turkish town on the Syrian border on Tuesday, wounding at least three people, a day after five were killed by fire from an area of Syria controlled by jihadists, a Turkish government official said.

In the last few weeks, Islamic State (IS) jihadists have repeatedly fired rockets at Kilis, the only town in Turkey where refugees from Syria's five-year conflict now outnumber local Turks.

Four rockets fired from Syria slammed into the southern Turkish town of Kilis on Monday, killing four Syrians including three children in the latest deadly cross-border strike to panic residents, officials said.

Kilis -- the only town in Turkey where refugees from the war in Syria now outnumber Turkish locals -- has been repeatedly hit by rocket fire from areas in Syria controlled by Islamic State (IS) jihadists in recent weeks.

Turkish police on Monday detained at least 105 people, including top construction executives, in a new crackdown on supporters of President Recep Tayyip Erdogan's arch foe, the U.S.-based preacher Fethullah Gulen.

Those detained are accused of providing financing for Gulen, who the Turkish government accuses of running a "terror organization" seeking to overthrow his former ally Erdogan.

The European Parliament sent a stern warning to EU membership candidate Turkey on Thursday, accusing its government of "backsliding" on democracy and the rule of law.

The parliament "is deeply concerned" that Ankara is violating criteria needed to join the European Union "in the light of the backsliding on respect for democracy and rule of law inside Turkey," a resolution approved by MEPs said.

Turkish President Recep Tayyip Erdogan on Thursday urged dozens of Muslim leaders gathered for a summit in Istanbul to end sectarian divisions in the Islamic world and join forces to fight terror.

Turkey is seeking to showcase its influence among the world's estimated 1.7 billion Muslims, particularly in lands once controlled by the Ottoman Empire, at the two-day summit of the Organization of Islamic Cooperation (OIC) which it will chair for the next two years.

Turkish authorities have arrested two suspected Russian secret agents over the assassination in Istanbul last November of a prominent figure from Russia's restive Caucasus region of Chechnya, reports said Wednesday.

Russian citizens Yury Anisimov and Alexander Smirnov have been placed under arrest by a Turkish court ahead of trial over the murder on November 1 last year of Chechen Abdulvakhid Edelgireyev in Istanbul, the Haberturk daily said.

German Chancellor Angela Merkel has no plans to travel to Turkey this week to inaugurate a new center for Syrian refugees, her spokesman said Wednesday, despite a previous announcement by Ankara.

The clarification by the spokesman, Steffen Seibert, about the trip announced last week by Turkish Prime Minister Ahmet Davutoglu comes amid soaring tensions over a vulgar satirical poem by German TV comic.

Saudi King Salman arrived in Turkey on Monday for a visit aimed at tightening increasingly close ties between the two overwhelmingly Sunni Muslim allies, receiving a lavish welcome that underlined the strength of relations.

The 80-year-old king was welcomed at Ankara airport by a delegation personally led by President Recep Tayyip Erdogan, in an unusual break from protocol and showing the importance Turkey attaches to the visit.

Pirates have attacked a Turkish cargo ship off the coast of Nigeria, kidnapping six crew members in a region increasingly hit by piracy in recent years, the Nigerian navy said on Monday.

"All the six Turkish crew members, including the captain of the vessel, the chief officer and the chief engineer, were abducted by the attackers," Nigerian Navy spokesman Chris Ezekobe told AFP.