(CNN) They are meant to be monitoring a ceasefire but are increasingly caught between the shots themselves.

Observers from the Organization for Security and Co-operation in Europe , or OSCE, have been given a mandate by all sides in the Ukraine conflict to keep track of weapons movements and to examine and record violations of a ceasefire, now in its 162nd day.

For the first time, an observer was wounded Monday near one of the worst front lines of the ceasefire whose constant violations -- allegedly by both sides -- has many asking when the fire will actually cease and when a full-blown conflict will begin again.

The OSCE said it is reviewing its operations in parts of the conflict zone as a result of what happened Monday and other incidents.

OSCE spokesman Michael Bociurkiw said there were incidents "very close together which did directly target the mission. That is a new phenomenon. The incidents were enough to make us press the pause button and review the situation."

In Monday's incident, the observer was hit with debris near Shyrokyne from what seemed like rocket-propelled grenade fire. His injuries weren't life-threatening.

Bociurkiw said he thought the rebel side was responsible but it was hard to tell if it was affiliated with any specific group.

On Sunday, an OSCE team was subjected to 90 minutes of shelling near Schastiye, with the firing coming from Ukrainian lines. Bociurkiw called it "a coordinated visit," meaning both sides were notified of the monitors' location and presence.

The observers have grown in number to more than 500 to monitor the implementation of the Minsk 2 accords , which slowed the conflict earlier this year.

Tension has built up, especially in the separatist-held areas of Eastern Ukraine's Donetsk region.

On Thursday, several hundred protesters marched on the hotel where the OSCE is based in the city of Donetsk, carrying placards with slogans such as "Your silence kills children" and "While you fatten, innocent civilians die."

Bociurkiw said he believes the protest was orchestrated but agreed that locals have genuine grievances over the shelling of their city that the OSCE is monitoring. The self-appointed mayor of Donetsk, separatist official Igor Martynov, led the protesters.

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Thirty OSCE vehicles were then damaged with spray paint and dollar bills daubed in red paint. OSCE observers spent hours cleaning the vehicles and checking them for booby traps.

Alexander Hug, deputy chief of the OSCE mission in Ukraine , later called the incident "an act of vandalism, not a protest."

Local residents expressed mixed feelings about the OSCE. The residents are under a form of economic barricade from the rest of Ukraine because of the difficulty of leaving and returning to separatist areas.

Anna, who didn't want her last name used due to the hostile environment, said monitors never come to her neighborhood but acknowledged the shelling stopped when they were in the city.

Ivan, who also declined to use his last name, said the mission was "quite useless." He only saw monitors in restaurants where, he pointed out sarcastically, it was hard to tell the direction from which shells were fired into the city.