ISTANBUL, TURKEY - In a sign of escalating frustration in Turkey after days of cross-border shelling with Syria, Prime Minister Recep Tayyip Erdogan lashed out against the United Nations' inaction with some of his strongest comments yet, saying world powers are repeating the mistakes they made in Bosnia in the 1990s.

"This negligence 20 years ago was explained by the international community being caught unprepared in dealing with the issues of the post-Cold War era," Erdogan said at an international conference. "Well, how can the injustice and weakness displayed in the Syrian issue be explained today?"

He said the world is witnessing a humanitarian tragedy in Syria and called for a change in the structure of the Security Council, where reluctance by any permanent member -- in this case, China and Russia -- can stymie action.

Tensions between Turkey and Syria, a former ally, have been rising for months, as Turkey has sheltered leaders of the armed opposition to the government of President Bashar Assad. But the bad feelings have intensified in recent days as shells from Syria began landing in Turkey, prompting retaliation, and as Turkish officials said they found Russian munitions on a Moscow-to-Damascus civilian jet they forced to land.

Russia has denied that weapons were onboard, saying the plane was carrying electronic components for a radar station.

On Saturday, the Russian newspaper Kommersant reported that the cargo had been sent by a company based in the Russian city of Tula that produces antitank, antiaircraft and anti-artillery systems, as well as radar equipment. The company, KBP Tula, was accused by the United States in 2003 of providing weapons to Iraqi leader Saddam Hussein, in violation of U.N. sanctions.

Later in the day, Syria's state-run news agency SANA said Syria has banned Turkish Airlines flights from its airspace.

On the Syrian side of the border in Idlib Province, fighting continued, with human rights activists saying the rebels had made progress in the area and had captured 200 people over the last week, including some military officers. The capture would be among the largest totals of people taken during a single battle.

The Syrian National Council, the main exile opposition group, has released a video explaining plans to reorganize and revitalize, including holding international elections. The group is planning meetings in Qatar as part of efforts to become more effective and relevant.