Dhaka: Bangladesh on Sunday mourned the victims of the attack on a cafe in Dhaka in which Islamic State terrorists killed 20 persons, mostly foreigners, one of them an Indian. The national flag would be hoisted at half-mast, people would wear black badges and prayers would be offered in mosques, temples, churches and other places of worship during the two days of mourning which started from Sunday, the Daily Star reported. At least seven IS militants stormed the Holey Artisan Bakery in Dhaka's diplomatic zone on Friday night, taking more than 30 people hostage. All the attackers were Bangladeshi citizens and five of them were wanted by police for various cases. Inspector General of Police Shahidul Hoque told CNN that police had previously tried to arrest five of the terrorists involved in the attack. The 20 persons were brutally murdered during the 12-hour long siege before Bangladeshi forces stormed the popular cafe and rescued 13 hostages, including one Japanese and two Sri Lankan nationals. As many as six terrorists were killed in the 50-minute army-led joint forces operation codenamed "Operation Thunderbolt" while one of the attackers was captured alive. The Islamic State militant group has claimed responsibility for the attack, saying its gunmen "killed 24 persons and injured more than 40 in the attack at a cafe in Dhaka". Two police officials were also killed in the gunfire earlier in the standoff, authorities said. According to the Bangladesh Army, those killed included nine Italian nationals, seven Japanese, one Indian girl, two Bangladeshis and a US citizen of Bangladeshi origin. Bangladesh Prime Minister Sheikh Hasina on Saturday, addressing the nation after the end of the siege, declared a two-day mourning for the victims. Hasina, condemning the "extremely heinous act", vowed to root out terrorism from the country which has seen a spate of deadly attacks by the IS and Al Qaeda-linked militants on progressive academics, writers, activists and religious minorities in the Muslim-majority country. "We'll establish Bangladesh as a peaceful state... No conspiracy can hinder our advancement," she said. "What kind of Muslims are these people? They don't have any religion. People must resist these terrorists. My government is determined to root out terrorism and militancy from Bangladesh," she said. Indian President Pranab Mukherjee, Prime Minister Narendra Modi and West Bengal Chief Minister Mamata Banerjee have condemned the attack. Modi called up Sheikh Hasina and condemned the "despicable attack" and said India "stands firmly with our sisters and brothers of Bangladesh" in this hour of grief. Indian External Affairs Minister Sushma Swaraj confirmed the killing of 19-year-old Tarishi Jain of Firozabad in Uttar Pradesh. The hostage crisis, the first-ever such incident in the country, began around 8.30 p.m. on Friday after the attackers carrying firearms, bombs and swords barged into the cafe. The gunmen, shouting "Allahu Akbar" raided the cafe and slaughtered those who were unable to recite the Quran, said rescued hostages. Later, the area was sealed off and following directives from Hasina, the armed forces along with the Rapid Action Battalion and police launched a rescue operation in the morning. The siege ended around 8.30 a.m on Saturday morning. The attack has also been condemned by other countries, including Pakistan, Malaysia as well as the European Union.