Lebanon’s anti-Syrian government on Tuesday claimed the first major breakthrough in the investigation into a series of attacks in the country over the last couple of years.

It announced the arrest of four Syrian members of an obscure Palestinian Islamic fundamentalist group for the bombing of two buses last month in the mountains north of Beirut.

The four suspects belong to the Fatah al-Islam group, said interior minister Hassan Sabeh. One member of the group is still being sought. Fatah al-Islam is said to have split off last year from the pro-Syrian Fatah Intifadah movement.

But Mr. Sabeh said they were still one and the same. “It is no secret that Fatah al-Islam is Fatah al-Intifada and Fatah al-Intifada has links to the Syrian intelligence-security apparatus,” Mr Sabeh told reporters.

But security expert Elias Hannah said that it was unclear who sponsored Fatah al-Islam. He also thought it unlikely that Fatah al-Islam had carried out the bus attacks without the benefit of a larger network.

The news of the arrests comes as the international community is making overtures to Damascus after having partly isolated Syria since 2005, mainly over its policies in Lebanon.

This week, for the first time in more than two years, an American assistant secretary of state visited Damascus and on Wednesday, the EU’s foreign policy chief, Javier Solana, will be in the Syrian capital.

Lebanon’s Western-backed government remains locked in a political struggle with the opposition, led by the pro-Syrian, Shia Hizbollah movement, which is demanding veto power in the cabinet.

The arrested men are said to have confessed to the near simultaneous bombings of two buses last month. Three people died and some twenty were wounded in the attacks in a Christian area that came on the eve of the second anniversary of the assassination of former Prime Minister Rafiq Hariri. The men also reportedly confessed planning other attacks.

Lebanon has been hit by a wave of attacks against prominent anti-Syrian politicians and journalists, as well as civilians, since the end of 2004.

This marks the first time that the security services have announced arrests of suspects who are said to be directly responsible for any of the attacks.

An ongoing UN investigation has implicated senior Syrian and Lebanese security officials in the murder of Mr. Hariri and has said that there are links with the other attacks. Four senior Lebanese security chiefs who were closely identified with the previously Syrian controlled state structure are in custody in connection with the assassination of Mr. Hariri.

Syria has vehemently denied involvement.