"Investigation has shown that an isolated extremist fundamentalist group made up of four people carried out an attack against the former building of the United Nations at Mazzih" in the west of the Syrian capital, the official SANA news agency said, quoting a ministry official.
"Two other Syrians helped this group to prepare the criminal attack," the official added.
Security forces arrested two men, Ahmad Shalash Hasan and Ezz Husain al-Husain, and killed two others, the official said.
A woman passerby and a policeman were killed in the gunbattle and three people, two of whom were police, were wounded.
One of those arrested, Hasan, said on Syrian television on Saturday the group was motivated to carry out the attack by "the blatant aggression by Israel and the United States and other infidel powers against Muslims in Palestine and Iraq."
The official, who asked not to be named, said "the same group, on 27 April, set fire to the public finance offices at Quneitra, some 60kms, southwest of Damascus, by using an explosive charge."
He claimed the attack was to cover up embezzlement of public funds by Aymam Shlash, an official there, who had stolen "more than 10 million Syrian pounds (about 200,000 US dollars)."
"Investigation has shown that an isolated extremist fundamentalist group made up of four people carried out an attack against the former building of the United Nations at Mazzih"
Syrian ministry official
Arms and explosives were later seized in two areas south of Damascus.
The official said the perpetrators and their accomplices had been put on trial and that the interior ministry would deal with any act aiming to undermine the security of citizens and stability of Syria.
On 3 May, a group calling itself the "Martyr Adib al-Kilani
Group", claimed responsibility for the attack, saying it targeted "senior officers and officials of the sectarian regime which carried out the most horrible massacres" in Hama, the town bombed in 1982 by the Syrian military to crush a Muslim Brotherhood uprising.
A vacant basement of the building targeted in the Damascus bomb attack in April belonged to Rifaat al-Asad, a disgraced uncle of President Bashar al-Asad who was in charge of security forces which suppressed the Hama revolt.