ISTANBUL — In a sign of escalating frustration in Turkey after days of cross-border shelling with Syria, Prime Minister Recep Tayyip Erdogan lashed out at the United Nations’ inaction in Syria 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 in Istanbul. ‘‘Well, how can the injustice and weakness displayed in the Syrian issue be explained today?’’
He also called for a change in the structure of the Security Council, where reluctance by any 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 and refugees from the fighting.
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 for an inspection.
Russia has denied that weapons were on board, saying the plane was instead carrying electronic components for a radar station and did not violate any international agreements.
The United States has said relatively little on the shipment, though Victoria Nuland, the State Department spokeswoman, said Friday that ‘‘we have no doubt that this was serious military equipment.’’
On Saturday, the Russian newspaper Kommersant reported that the cargo had been sent by a company based in Tula that produces antitank, antiaircraft, and antiartillery systems, as well as radar equipment. The company identified, KBP Tula, was accused by the United States in 2003 of providing weapons and sophisticated military equipment to the Iraqi leader Saddam Hussein, in violation of UN sanctions.
On the Syrian side of the border with Turkey, fighting continued Saturday in Idlib province, with human rights activists saying that the rebels had made further progress in the area. Activists also said the rebels had moved deeper into the neighboring province of Latakia, one of the remaining strongholds of support for Assad.
The Syrian Observatory for Human Rights, an antigovernment group, said rebels reported shooting down a Syrian fighter jet Saturday. An online video showed wreckage, but neither the report nor the video could be confirmed because of Syria’s tight restrictions on journalists.
Jockeying for control of the opposition movement has also continued. The Syrian National Council, the main exile opposition group, appeared to be taking steps to try to revitalize itself amid charges that it had become irrelevant, was unable to effectively lead a revolt from outside the country and was dominated by Islamists.
The group released a video on Friday that promised international elections for its own leadership, but did not explain important specifics including whether or how it intended to hold a vote in war-torn Syria.