BEIRUT, July 20 (Reuters) - A funeral ceremony was held on Friday for three of Syrian President Bashar al-Assad's senior security officials who were killed in a bomb attack, but the Syrian leader stayed away from the sombre procession.

Assad was represented by Vice President Farouq al-Shara at the ceremony, shown on state television news.

The attack on a meeting of Assad's inner circle on Wednesday killed his brother-in-law Assef Shawkat, Defence Minister Daoud Rajha and veteran army general Hassan Turkmani.

The three men's coffins, draped in the Syrian flag, were driven in black hearses behind three huge wreaths of flowers carried by military officers towards the Tomb of the Unknown Soldier on Mount Qasioun, overlooking the capital.

Only senior military officers, government officials and close relatives were in attendance.

A fourth Syrian official, intelligence chief Hisham Bekhtyar, has died of wounds suffered in the Damascus bombing, the government said on Friday.

Assad has made only one appearance since the attack, adding to the sense of a challenge to his authority. On Thursday he was shown on television swearing in a new defence minister to replace Rajha.

After the funeral ceremony on Friday, Rajha's body was taken to a Damascus church where people from all sects prayed for the former defence minister, a Christian, before he was buried, witnesses said.

Shawkat's body was expected to be taken to his home village near the Mediterranean city of Tartus for burial, residents said.