BEIRUT (Reuters) - Tens of thousands of Syrian Kurds called on Saturday for the overthrow of President Bashar al-Assad during the funeral in eastern Syria of a Kurdish opposition figure who was killed a day earlier.

British-based Syrian Observatory for Human Rights said the funeral came under fire and at least one mourner was killed and three wounded. It said at least 50,000 people had turned out for the funeral but it was unclear who opened fire.

Meshaal al-Tammo, a charismatic figure who was released from jail earlier this year, was a critic of Assad who had also angered powerful Kurdish parties because of his criticism of Kurdish rivals. The United States has condemned his killing.

Video footage broadcast by al Jazeera television showed Tammo's coffin being carried on people's shoulders wrapped in a Kurdish flag and covered with flowers.

"Leave, Leave," the mourners chanted.

Activists said four gunmen burst into a house in the city of Qamishli, shot dead Tammo and wounded his son. It was not clear who was behind the attack.

Fares al-Tammo, Meshaal's son, told al-Jazeera from Erbil in northern Iraq, that the Kurds were angry and blamed the Syrian authorities for his father's death.

"This blood is precious to them (Kurds), they will not give up until the regime is overthrown and the execution of Bashar al-Assad."

Activists in Damascus said Syrian authorities stepped up security in Kurdish areas in the capital.

Kurds make up about 10 percent of Syria's 20 million population and largely support the uprising against Assad.

Ethnic Kurds have long complained of discrimination and staged violent protests against Assad in 2004. Kurds are not allowed to teach Kurdish in schools or set up Kurdish radio stations.

While Assad has sent troops and tanks to crush protests against him which erupted in March, he also promised reforms. He has ended a state of emergency and promised parliamentary election in February.

He tried to pacify the Kurds by giving citizenship to tens of thousands of them and casualties in the Kurdish areas remained the lowest.

Many of Assad's opponents say his reform promises are hollow and that his government has forfeited all legitimacy after killing at least 2,900 civilians, by a U.N. count.

(Reporting by Mariam Karouny Editing by Maria Golovnina)