A member of the Arab League observer team in Damascus told Al Arabiya broadcaster Monday that "what's happening in Syria is genocide."
"This is a regime is taking revenge on its people," MostasharMahgoub told the channel by telephone.
Mahgoub was injured in security forces shelling in Homs city activists said. However, he refused to say how and where he was wounded and it was also not clear whether he was in the restive city of Homs or in Damascus during the call.
Around 50 Arab League monitors, headed by Sudanese General Mohammed al-Dabi, began arriving in Syria to start inspecting areas gripped by violence, according to activists.
According to an Arab diplomat based in Beirut "preparations were being made for the observers to go to Homs on Tuesday, but due to the current situation, intensive contacts are being made to speed the visit."
Homs, in central Syria, has been a focal point of the government crackdown on anti-government demonstrations. A nine-member advance Arab team arrived in Damascus last week, to prepare for the monitors.
The arrival of the observers in Syria is part of a deal agreed to by President Bashar Assad's government with the Arab League last week.
It calls for the withdrawal of the Syrian army and militias as well as rebel forces from the streets, the release of detainees and an end to all forms of violence. A total of 150 Arab monitors are due to arrive in Damascus by the end of the month.
During the Monday shelling in Homs, at least 25 people were killed, Homs-based activist Omar Homsi told dpa by phone. He said that 21 of them are from the Baba Amr neighborhood, where 20 houses were destroyed.
Some 40 others were wounded, most them women and children, he said, adding that most of the injured could not be taken to the hospitals due to the intensity of the shelling.
"The situation is frightening and the shelling is the most intense of the last three days," the London-based Syrian Observatory for Human Rights said in a statement.
"The observers must head immediately to the martyrs' district of Baba Amr to stop the assassinations and meet with the people so that they witness the crimes being perpetrated by the Syrian regime," the group said.
Activists posted gruesome pictures of human remains on the streets inside the Baba Amr neighborhood on their websites.
Footage posted online showed the aftermath of the shelling, with bleeding corpses of at least four young men and a woman screaming for help from the international community.
Omar Idlibi, a prominent Syrian activist in exile, expressed dismay over the mission of the observers and blamed the Arab League for the delay in their mission."
"Scores of people are being killed in the streets and the Syrian government is still stalling and the Arab League is still not doing anything," Idlibi said.