Bomb explosions killed at least 15 people and wounded dozens on Tuesday in a Damascus district populated mostly by members of Syrian President Bashar al-Assad's Alawite sect, opposition activists said.

Syrian state media said an explosion hit the district of Hai al-Wuroud, in the northwest of the capital, causing an unspecified number of deaths and injuries.

Activists said three bomb explosions were heard and smoke was seen rising from the area in the latest tit-for-tat attack. The hilltop neighborhood is situated near a barracks and housing for elite army units.

A bomb attack on Monday in the western "Mezzeh 86" district of Damascus killed 11 people and wounded dozens more, Syrian state media reported.

Seif al-Sham, an Islamist rebel unit, claimed responsibility for that attack, which targeted what it described as a meeting point for the army and police, as well as the shabbiha (ghost) militia loyal to Assad.

Damascus has several hilltop enclaves mostly inhabited by members of the Alawite minority, a sect of Shi'ite Islam that has dominated Syria, which has a Sunni Muslim majority, since the 1960s.

"After bomb attacks and constant ground aerial bombardment on Sunni districts, it seems Alawite areas are now considered fair game," Nawara al-Soueid, an opposition activist in the capital, said.

Last month several bombs exploded during the Muslim Eid holiday near mosques in Sunni districts and the Damascus suburbs, killing or injuring dozens of people, activists said.

Earlier Tuesday, gunmen shot and killed the brother of Syria's parliament speaker as he drove to work in the capital Damascus on Tuesday, the state-run news agency reported.

Mohammed Osama Laham, brother of Parliament Speaker Jihad Laham, was killed in the Damascus neighborhood of Midan, the SANA news agency said.

It was the latest in a wave of assassinations targeting Syrian officials, army officers and other prominent supporters of President Bashar Assad's regime. Four of the president's top security aides were killed in a rebel bombing of state security headquarters in Damascus on July 18.

The killing came a day after some of the most intense fighting in Damascus in months as rebels wage a civil war to unseat Assad.