UN Secretary General Ban Ki-moon has said bomb attacks, such as the one near a UN convoy in Syria today, cast doubt on the future of the ceasefire monitoring mission in the country.

The roadside blast at a military checkpoint near the protest city of Deraa injured 10 Syrian troops escorting UN observers.

Mr Ban expressed deep concern at the growing use of roadside and other improvised bombs across Syria.

However, there was no immediate evidence that UN monitors in the convoy were the target of today's attack.

"Such incidents, in addition to the continued violence reported in many cities in Syria, call into question the commitment of the parties to the cessation of violence and may have a direct impact on the future of the (UN) mission," Mr Ban said in a statement released by UN spokesman Martin Nesirky.

"We have no evidence to believe that the explosion was intended to target the UNSMIS convoy; however, this incident demonstrates the difficult and challenging conditions under which our United Nations observers are operating," said Mr Ban.

He said it also demonstrates the volatile situation in which the Syrian people have been living for months.

Mr Ban said he strongly condemned today's attack and called on all parties to adhere to the cessation of violence and to cooperate with, support and protect the UNSMIS observers.

The UN Secretary General reaffirmed that the UN mission and efforts of UN-Arab League envoy Kofi Annan "are possibly the only remaining chance to stabilize the country and avert a civil war."

There are now 70 military observers and 43 civilian staff in the UN Supervision Mission in Syria (UNSMIS).

The mission was set-up by the UN Security Council to monitor a shaky cessation of hostilities that started on 12 April.

The UN says well over 9,000 people have been killed in Syria since an uprising against President Bashar al-Assad started in March 2011.