KIEV, July 28 - The OSCE's special mission to Ukraine on Tuesday made a fresh appeal to all sides in the military conflict in Ukraine's east to guarantee safe conditions for its monitors after one of its officers was wounded during an exchange of fire.

"We have come under fire countless times... despite the fact that all sides know about our presence," Alexander Hug, the deputy head of the OSCE's monitoring mission (SMM) said at a televised briefing, Reuters reported.

The mission said in a report that an SMM patrol leader was struck on Monday by concrete debris caused by an explosion which hit the mission's car near Shyrokyne, a small town near the strategic port of Mariupol.

The SMM is monitoring the implementation of a peace agreement between Ukraine and pro-Russian rebels. OSCE deployed the mission of unarmed civilian observers to Ukraine in March 2014.

The SMM has accused both sides of failing to respect the ceasefire by not fully withdrawing their heavy artillery as required by the peace agreement, which was brokered in February to end a conflict in which over 6,500 people have been killed.

"If we are not afforded safe and unrestricted access we are unable to fulfill our mandate," Hug said.

Last week about 300 people held a protest against the OSCE in rebel-held Donetsk, in what the security watchdog said was an orchestrated move to restrict its work.

The protesters, mainly women, arrived at hotel in two buses accompanied by the city's separatist mayor Igor Martynov. A Reuters witness said they spray-painted peace slogans on the cars belonging to the OSCE.

The OSCE said the crowd was protesting the deaths of civilians in shelling despite a ceasefire deal and also against the work of the OSCE, which is monitoring the implementation of a peace agreement between Ukraine and pro-Russian rebels.

"We have to limit our movements in the aftermath," said Hug, condemning the "orchestrated" protest as a "type of censorship of our activity that is not acceptable." (rt/ez)