Syria's main Western-backed opposition group on Tuesday welcomed an EU decision to place the military wing of Hezbollah on the bloc's terror list as a "step in the right direction," and called for the Lebanese militant group's leaders to be put on trial for their role in the Syrian civil war.

Hezbollah, a staunch ally of the Syrian regime, has sent its fighters to bolster President Bashar Al-Assad's forces in their assault on rebel-held areas in Syria. The group was instrumental in helping government forces seize the strategic town of Qusair near the Lebanese border last month, and its members are believed to be fighting alongside regime forces in the central province of Homs.

The Shia group's role is highly divisive in Lebanon and has outraged the overwhelmingly Sunni rebels fighting in Syria to topple Assad.

The EU's 28 foreign ministers placed Hezbollah's military wing on its terror list on Monday after prolonged diplomatic pressure from the US and Israel, which consider the group a terrorist organization.

Some European countries had pushed for EU action, citing a terrorist attack in Bulgaria's Black Sea resort of Burgas last year that killed five Israeli tourists and a Bulgarian.

Hezbollah's military wing was accused of involvement, an allegation it denied. In March, a criminal court in Cyprus found a Hezbollah member guilty of helping to plan attacks on Israelis on the Mediterranean island.

But several EU nations have pointed to Hezbollah's involvement in Syria as further reason for the move.

The Syrian National Coalition, the main opposition umbrella group, hailed the EU decision but stressed the need for European countries to take "concrete steps that would contribute to stopping the militia's involvement in Syria."

"We call for Hezbollah leaders to be put on trial for the terrorist crimes they committed on Syrian territory," the SNC said in a statement.

It did not say where they should face trial, and the prospects of senior Hezbollah figures ever appearing in a courtroom to answer for the Iranian-backed group's role in Syria appear dim.