UNITED NATIONS, May 14 (Xinhua) -- The Security Council on Monday condemned "in the strongest terms" the terrorist attacks in Indonesia on Sunday and Monday, which resulted in at least 18 deaths and dozens of injuries.

The members of the Security Council expressed their deepest sympathy and condolences to the families of the victims and to the government of Indonesia and they wished a speedy and full recovery to those who were injured, said the council in a press statement.

The members of the council underlined the need to hold perpetrators, organizers, financiers and sponsors of these reprehensible acts of terrorism accountable and bring them to justice. They urged all states to cooperate actively with the Indonesian government and all other relevant authorities in this regard.

The council members reaffirmed that terrorism in all its forms and manifestations constitutes one of the most serious threats to international peace and security, and asked all states to combat by all means threats to international peace and security caused by terrorist acts.

The terrorist attacks in the city of Surabaya on Sunday and Monday were carried out by three families, said Indonesian police.

On Monday, a family of five riding on two motorbikes attacked the police headquarters in the Indonesian city. Four members of the family died in the suicide bombing, which also injured six police officers and four civilians.

On Sunday, a family of six, including their four young children, detonated bombs in three churches in Surabaya, killing themselves and eight other people. Some 40 people were injured.

Later Sunday, a mother and her 17-year-old daughter were killed in a Surabaya suburb when a bomb handled by the father of the family detonated prematurely. Police described the incident as a terror act.

UN Secretary-General Antonio Guterres, in the wake of the church bombings on Sunday, said through his spokesman that he was appalled at the fact that children were used to participate in the attacks.