Syria's largest mainstream opposition group will attend U.N.-brokered talks in Geneva, a senior delegate told AFP on Friday after four days of discussions in Riyadh.

The delegate said the Saudi-backed High Negotiations Committee will send "about 30, 35 people" in all to Geneva, where talks got underway Friday.

Russia said on Thursday it wanted to hold an international meeting on Syria -- including key players from the West and the Middle East -- in Munich next month.

"There is an agreement in principle between Russian Foreign Minister Sergei Lavrov and Secretary of State John Kerry, and now we will propose to all the other participants of the international Syria support group a time and place -- Munich, February 11," state news agency TASS quoted deputy foreign minister Mikhail Bogdanov as saying.

Al-Qaida's affiliate in Syria, Al-Nusra Front, has boosted its presence in the country's divided former economic capital of Aleppo, a monitoring group said on Wednesday.

The Syrian Observatory for Human Rights said Al-Nusra has erected new positions in several districts of the northern city after having sent in a convoy of 200 vehicles loaded with fighters.

Only Syrians have been invited to peace talks in Geneva, the U.N. said Wednesday, in an apparent contradiction to Turkey's suggestion that it would be included.

On Tuesday, Turkish Foreign Minister Mevlut Cavusoglu said Ankara would "boycott" the talks set to open on Friday if the Syrian Kurdish group Democratic Union Party (PYD), which Ankara believes is linked to militants fighting inside Turkey, was at the negotiating table.

Warring Syrian parties expected in Geneva for peace talks this week must agree to "tear down the Berlin Wall" blocking aid workers from reaching besieged Syrians, a senior humanitarian leader urged Tuesday.

Jan Egeland, the head of the Norwegian Refugee Council, and U.N. officials said they were willing to talk with any faction, including the Islamic State group (IS), if it helped deliver life-saving aid to victims of the conflict.

The United Nations on Tuesday sent out invitations to new Syria peace talks in Geneva this week, as leading opposition representatives debated whether to attend.

U.N. Syria envoy Staffan de Mistura's office said it had issued invitations to the talks, which are scheduled to begin on Friday, but without saying who had been invited.

Syria's leading opposition coalition is to decide Tuesday whether to attend peace talks in Geneva, following a tense meeting with U.S. Secretary of State John Kerry, a member told AFP on Monday.

The member of the so-called High Negotiations Committee said Kerry applied "pressure" during a weekend meeting in Saudi Arabia, warning the opposition risked "losing friends" if they failed to attend the talks.

At least 11 Islamist fighters and five civilians were killed as a ballistic missile struck a building in northwest Syria during a meeting between rebel groups, a monitor said Monday.

"Eleven fighters from (Al-Qaida affiliate) Al-Nusra Front and other Islamist groups were killed on Sunday, along with five civilians, when a ballistic missile hit a police station being used as a court in Salqin" in Idlib province, the Syrian Observatory for Human Rights said.

Suspected Russian raids killed 33 civilians in war-ravaged eastern Syria on Saturday, amid reports US forces are building up an air base to bolster their fight against jihadists further north.

Meanwhile, senior diplomats scrambled to resolve the key question of who will represent Syria's opposition at crucial talks next week aimed at ending the nearly-five year war.

Turkish President Recep Tayyip Erdogan on Friday expressed alarm over reports of a build-up of Russian troops in northern Syria near the Turkish border, saying such movements would not be tolerated.

"We have said this from the beginning: we won't tolerate such formations (in northern Syria) along the area stretching from the Iraqi border up to the Mediterranean," Erdogan told reporters after Friday prayers in Istanbul.