BEIRUT, Lebanon — Syrian security forces on Friday attacked two prominent opposition leaders, shooting one to death in the north and beating another in broad daylight in the heart of the capital, Damascus, activists said.

Mashaal Tammo, 53, a leading Kurdish political figure, was killed by four masked gunmen who stormed his house in Qamishli, in northern Syria, activists said. His son, Marcel, and another activist, Zahida Rashkilo, were wounded. Both are members of the liberal Kurdish Future Movement Party, which Mr. Tammo founded and which considers the minority Kurdish community an integral component of Syrian society.

In Damascus, Riad Seif, a dissident and a former political prisoner, was beaten by government security operatives as he left Al Hassan Mosque in the neighborhood of Midan, activists said.

The official Syrian Arab News Agency carried a strikingly different account of Mr. Tammo’s death, calling him a “nationalistic opposition leader” who was assassinated by “gunmen in a black car.”