BEIRUT — A nationwide Syrian cease-fire brokered by Russia and Turkey that went into effect at midnight held Friday despite minor violations, marking a potential breakthrough in a conflict that has disregarded high-level peace initiatives for over five years.

The Britain-based Syrian Observatory for Human Rights reported clashes early Friday between troops and rebels in the central province of Hama and near the capital, Damascus. It said that later in the day a man was killed by sniper fire in eastern suburbs of Damascus, becoming the first fatality since the truce went into effect. The group also reported an aerial attack on the rebel-held Barada Valley near Damascus.

The Syrian army denied reports it was bombarding the Barada Valley region saying opposition claims aim to show that the army is not abiding by the truce.

Opposition activist Mazen al-Shami, who is based in the Damascus suburb of Douma, said minor clashes nearby left one rebel wounded. Activist Ahmad al-Masalmeh, in the southern Daraa province, said government forces had opened fire on rebel-held areas.

Several past attempts at halting the fighting have failed. As with previous agreements, the current cease-fire excludes both the al-Qaida-affiliated Fatah al-Sham Front, which fights alongside other rebel factions, and the Islamic State group.

Russian President Vladimir Putin said Thursday that the cease-fire will be guaranteed by both Moscow and Turkey, and the agreement has been welcomed by Iran. Moscow and Tehran provide crucial military support to Syrian President Bashar Assad, while Turkey has long served as a rear base and source of supplies for the rebels.

If it holds, the truce between the Syrian government and the country’s mainstream rebel forces will be followed by peace talks next month in Kazakhstan, Putin said in announcing the agreement. He described it, however, as “quite fragile” and requiring “special attention and patience.”