BEIRUT (AP) — A cease-fire has brought relative quiet to parts of Syria for the first time in years.

There have been numerous violations, but the U.N. envoy for Syria calls the situation so far "quite reassuring."

Staffan de Mistura says "the first night and first day certainly gave the impression that everyone is serious in their commitment to keep on going with this cessation of hostilities."

He says cease-fire monitors will work to improve the way they verify incidents and prevent them from escalating.

A top military official in Moscow said Russia has grounded its warplanes in Syria to help secure the cease-fire, which took effect at midnight.

Lt.-Gen. Sergei Rudskoi said that while Russia will continue airstrikes against the Islamic State group and the Nusra Front, al-Qaida's branch in Syria, which are not observing the cease-fire. But he said Moscow is keeping its aircraft on the ground for now "to avoid any possible mistakes."

Rudskoi said the Russian military had established hotlines to exchange information with the U.S. military in order to help monitor the cease-fire and quickly respond to any conflict situations.

The Islamic State group launched a surprise offensive on a northern town and carried out a suicide truck bombing in central Syria.