JAKARTA, May 13 (Xinhua) -- Six people were killed and at least 35 others injured as suicide bombers blew themselves during congregations in three churches in Surabaya city, capital of Indonesia's East Java province, on Sunday, provincial police spokesman Frans Barung told media.

The deadly blasts took place in Santa Maria church in Ngagel Madya area, Gereja Kristen Indonesia church on Diponegoro street and Pantekosta church on Arjuno street, the police spokesman said.

The first explosion took place at 07:15 a.m. Jakarta time and was followed by others with the interval time of about five minutes, according to the police.

The attackers, disguising as followers of the morning sermon in the churches, detonated bombs which hit scores of followers, said the police spokesman.

The police have cordoned off all the scenes for investigation, said Barung.