BEIRUT -- Russia's Defence Ministry announced a ceasefire for a third safe zone in war-torn Syria on Thursday, paving the way for the delivery of sorely needed humanitarian relief to rebel-held areas north of the city of Homs.

Military Spokesman Maj. Gen. Igor Konashenkov said Russia would deploy military police in the area on Friday and set up two checkpoints and three observation points around its borders.

"It's important that people can live again," said Mustapha Khaled, an opposition activist working for a media centre for the town of Talbisah, in north Homs province.

It is the third of four planned ceasefires reached in recent months under an agreement brokered by Russia, Iran, and Turkey in May that aims to "de-escalate" the violent and prolonged Syrian civil war.

Russia and Iran are providing military support to President Bashar Assad, while Turkey sponsors some of the opposition forces arrayed against him.

Pro-government forces have besieged the enclave north of Homs for years, but have been unable to capture it from the opposition even as it recovered territory elsewhere.

Shelling and air strikes against the enclave have eased since the May agreement was signed, said Khaled. Residents will now be expecting further relief.

The agreement, according to notes leaked by the British-based Syrian Observatory for Human Rights monitoring group, follows the model of another ceasefire zone for the suburbs of Damascus.

Both truces were negotiated in Cairo between Russia and what the Ministry of Defence described as the "moderate opposition."

Aid will be expected to flow again to north Homs, and Russia will man checkpoints around the enclave to facilitate the movement of civilians in and out of the enclave to revitalize the economy.

The agreement also prescribes the release of political prisoners, long a demand of the opposition.

The UN has long pleaded with the sides in Syria to allow relief to flow to besieged areas. It says the parties are using food and other basic goods as a weapon of war. Pro-government forces have been responsible for most of the obstructionism.

The north Homs enclave holds 147,000 people, according to the military media arm of the Lebanese militant group Hezbollah, a participant in the conflict.

The government's air force has cut back its attacks on the four "de-escalation zones" designated in the May agreement.

There are still loopholes for fighting however, characteristic of the ceasefires that have come and gone throughout the war. The government has pounded parts of the Damascus suburbs nominally covered under the ceasefire there, on the grounds that it is targeting al Qaeda-linked militants, as permissible in the agreements.

The Observatory says 170 people have been killed in the 12 days since the ceasefire there went into effect, calling the truce a "failure." Other such ceasefires have crumbled under the strain of these attacks.

Also Thursday, a 117-bus convoy from Lebanon carrying thousands of refugees and al Qaeda-linked militants arrived at a transfer point in the western Syrian province of Hama, en route to the rebel-held Idlib province in northwest Syria. Idlib is dominated by a Syrian affiliate of al Qaeda.

The buses will be released toward the north in staggered groups as the militants in Idlib release prisoners from the Lebanese militant group Hezbollah, which is fighting in support of Assad's government in Syria.

The swap is part of an agreement struck this week to provide al Qaeda-linked militants with safe passage out of Lebanon. Some 6,000 Syrians elected to leave Lebanon with the fighters. It followed two weeks of battles between Hezbollah and the Syrian government on the one side, and the al Qaeda-linked militants on the other, along the frontier between Lebanon and Syria.

Associated Press writer Nataliya Vasilyeva in Moscow contributed to this report