Damascus. A bomb blast in the centre of the Syrian capital, Damascus, has killed at least two people, according to reports.Syrian state news agency Sana said a suicide bomber had blown himself up in al-Jisr al-Abyad district.The UK-based Syrian Observatory for Human Rights (SOHR) said two people had been killed in the attack. State media put the death toll higher.The activist network said the target of the explosion appeared to be a government building.Rami Abdulrahman, director of the SOHR, was quoted by Reuters as saying the office was an administrative site used by relatives of dead soldiers, and that it was not a military facility.At least 17 people were injured in the blast, according to Sana.Meanwhile, opposition fighters have abducted 12 nuns from the ancient Christian town of Maaloula, according to church officials.Syrian rebels captured large parts of Maaloula, around 60 km (40 miles) northeast of the capital, on Monday after three days of fighting.Damascus is experiencing increasing violence as clashes between government forces and rebels in the suburbs intensify.At least 15 people were killed and more than 30 were wounded in a suicide bomb attack at a bus station in the western Soumariya district of the capital last week, state media and activists said.The UN says more than 100,000 people have been killed since the uprising against President Bashar al-Assad began in 2011.More than 2.2 million Syrians have fled to neighbouring countries, while an estimated 4.25 million have been displaced internally.