U.S. President Barack Obama and Turkish Prime Minister Recep Tayyip Erdogan agreed Sunday on the need to send "non-lethal" aid to Syrian rebels, including communications equipment, a U.S. official said.

The two leaders agreed that a "Friends of Syria" group meeting on April 1 should seek to provide such aid and also medical supplies, as they met in South Korea on the eve of a nuclear security summit, said U.S. deputy national security adviser Ben Rhodes.

The head of the rebel Free Syrian Army, Riad al-Asaad, announced Saturday the formation of a military council grouping all rebel chiefs, including Syria's most senior army deserter General Mustafa al-Sheikh.

The council "is a step towards guaranteeing the unity of the troops and armed forces (of the opposition) on Syrian territory," Colonel Asaad told Agence France Presse by telephone from Turkey.

Two Turkish journalists who have been missing in Syria for about two weeks are safe, according to an Islamic charity which said Saturday it was in negotiations to secure their return home.

"We are certain that they are alive and in good health," Bulent Yildirim, head of the IHH Humanitarian Relief Foundation, told the Anatolia news agency.

Several Syrian opposition groups will gather in Turkey on Monday to hammer out common objectives in the face of the regime's deadly crackdown on dissent, the main umbrella grouping said.

The Istanbul meeting comes ahead of the second "Friends of Syria" conference in the same city on April 1, the Syrian National Council said in a statement on Saturday.

Fifteen rebel Kurds, all of them women, were killed in fighting with Turkish security forces in the southeast of the country on Saturday, the interior ministry said.

The clashes took place in a rural area of the province of Bitlis, a center of the armed rebellion being waged by the outlawed Kurdistan Workers' Party (PKK), according to a statement carried by the official Anatolia news agency.

An international action plan is needed to stop the "human tragedy" in Syria, Turkey's foreign minister said Thursday after a U.N. Security Council statement calling for all sides to end violence.

"In addition to a common message we also have to develop a joint plan of action," Ahmet Davutoglu said after talks in Vienna with his Austrian counterpart ahead of an EU foreign ministers' meeting in Brussels that he will attend.

Six Kurdish rebels and six policemen have been killed over the past two days in a massive sweep against Kurdish rebels in southeastern Turkey, security sources told Agence France Presse on Thursday.

Backed by helicopters, thousands of security forces, including police and the army, were participating in the largest anti-rebel operation so far this year, they said.

Turkey's energy minister said Wednesday negotiations were under way to earn waivers from U.S. sanctions on crude oil imports from neighboring Iran.

"Currently talks are being conducted at the level of companies," Taner Yildiz was quoted as saying by the Anatolia news agency.

Twenty-four people were wounded Tuesday when Turkish police used water cannon and tear gas against Kurdish demonstrators gathered for the community's New Year, a security source said.

The latest clashes erupted two days after New Year festivities in Istanbul and elsewhere saw at least nine people injured.

Turkey said Tuesday it was bringing forward by a day to April 1 a "Friends of Syria" conference in Istanbul, designed to pressure the Damascus regime into halting its crackdown on opponents.

"We have decided to bring the meeting forward for technical reasons," a Turkish diplomat said of the gathering originally set for April 2.