The head of a Syrian military hospital has been killed by members of an "armed terrorist group" in the capital Damascus, the state news agency says.
Three men opened fire on Brig-Gen Dr Isa al-Kholi as he left his home in the north of the city, it said.
It is believed to be the first assassination of a senior officer in the capital since the uprising began.
The attack came as activists said 15 people had died as tanks and artillery continued to bombard the city of Homs.
The fatalities were reported in the Baba Amr district - a centre of anti-government protests - but residents said there had also been explosions and heavy gunfire in the neighbouring area of Inshaat.
After a week under shellfire and virtual siege, conditions in Homs are reported to be getting desperate, with basic supplies running low.
Activists say more than 400 people have been killed since security forces launched an assault on opposition-held areas in Homs last Saturday.
Human rights groups say more than 7,000 have died nationwide since March. The government says at least 2,000 members of the security forces have been killed combating "armed gangs and terrorists".
The Syrian state news agency, Sana, reported that Brig-Gen Kholi, director of Hamish military hospital and a specialist in orthopaedics, was shot dead outside his home in Rukn al-Din district on Saturday morning.
It did not give further details, but published a photograph of the bloodied body of a man who appeared to have been shot in the neck.
No group has said it was behind the killing.
The BBC's Jim Muir in Beirut says that although several officers of similar rank have been killed in combat in recent weeks, this is believed to be the first assassination of such a senior military figure in Damascus since protests against President Assad erupted in March.
The violence came a day after state media said 28 people had been killed in two suicide car bomb attacks in the northern city of Aleppo.
State television blamed the bombings on what it described as "armed terrorist gangs", which it said had targeted a Military Intelligence complex and a riot police base but killed civilian bystanders, including children.
The deputy leader of the rebel Free Syrian Army (FSA), a group of army defectors based in Turkey, told the BBC that its fighters had been attacking the bases at the time, but were not responsible for the blasts.
US officials are reported to believe that two recent bombings in Damascus were carried out by militants from al-Qaeda in Iraq, and that the Sunni extremist group was also likely behind the attacks in Aleppo.
The officials cited US intelligence reports, which appeared to support President Assad's accusation that al-Qaeda was involved in attacks on Syrian government forces, according to the McClatchy Newspapers.
The overall leader of al-Qaeda, Ayman Zawahiri, was believed to have authorised al-Qaeda in Iraq's operations in Syria, the officials said.
"This was Zawahiri basically taking the shackles off," one added.
Meanwhile, the United Nations General Assembly is becoming the focus of attempts to apply pressure on the Syrian authorities.
Saudi Arabia is circulating a draft resolution among its members, similar to the one vetoed in the Security Council by China and Russia.
The draft resolution circulated by Saudi Arabia "fully supports" the Arab League peace plan published last month, which called on Mr Assad to hand over power to his vice-president, and make way for the rapid formation of a national unity government including the opposition.
While urging all sides to end the violence, it lays blame primarily on the Syrian authorities, which are condemned for "continued widespread and systematic violations of human rights and fundamental freedoms".
There is also a request for Secretary General Ban Ki-moon to appoint a special envoy to promote a peaceful solution to the crisis - a proposal that Arab League Secretary General Nabil al-Arabi made this week.
The General Assembly is scheduled to discuss Syria on Monday, when it will be addressed by the UN's High Commissioner for Human Rights, Navi Pillay, but no vote on the resolution is expected by then.
There is no power of veto at the General Assembly but its resolutions have no legal force, unlike those of the Security Council.