New Delhi - Islamic extremists in Bangladesh hurled homemade bombs and traded gunfire with police guarding an Eid prayer service attended by hundreds of thousands of people on Thursday, killing two officers, a woman and an assailant.The violence occurred just days after a deadly hostage-taking at a Dhaka restaurant that left 28 dead, most of them foreigners. The attacks are an escalation in extremist violence that had previously mostly targeted individual atheist bloggers, religious minorities and others considered by militants to be "enemies of Islam."Thursday's attack hit the sprawling Sholakia grounds as huge crowds of people attended a prayer gathering for the Muslim holiday of Eid-al-Fitr, marking the end of the fasting month of Ramadan, in Kishoreganj district, about 90km north of Dhaka, the capital.At least one of the bombs hurled toward a patrolling police convoy exploded, killing two officers, assistant police superintendent Tofazzal Hossain said.The assailants then exchanged gunfire with police, and a woman and an assailant were killed, Hossain said.Police chased the assailants through the area, searching nearby homes and body searching some devotees at the gathering, said resident Shafiqul Islam, who was among those offering Eid prayers.More than a dozen other people received gunshot or bomb shrapnel wounds, including two who were in critical condition, he said.There was no immediate claim of responsibility. The information minister said police had been the target and insisted the attack was carried out by domestic militants fighting to destabilise Prime Minister Sheikh Hasina's government and establish Islamic rule in the Muslim-majority nation."It is a totally political move. They are out to destabilise the government. It is a political attack to oust and topple the secular government of Sheikh Hasina," Minister Hasanul Haq Inu told Indian broadcaster CNN-News 18.The government has dismissed claims of responsibility by the Islamic State group (ISIS) for past attacks, including last Friday's hostage-taking. Bangladesh authorities say those claims are opportunistic grabs at global attention, and that none of the attacks has been orchestrated from abroad.Instead, Hasina's government has accused her political opponents of backing the militants' agenda, an allegation the opposition parties deny.ISIS videoOn Wednesday, the Islamic State group released a video warning of more attacks in Bangladesh, according to the SITE Intelligence Group, which monitors jihadi activity online.Meanwhile, authorities were continuing to investigate Friday's attack by a group of young Bangladeshi men who were later identified as coming from well-off families. The attackers held about 35 hostages overnight, torturing and killing 20 of them, including 17 foreigners from Japan, Italy and India.Prime Minister Hasina pleaded with families across Bangladesh on Thursday to report to police if any of their sons have gone missing in recent months, as the hostage-takers had before staging their restaurant attack in Dhaka's diplomatic quarter.Many Bangladeshis have said they are horrified by the violence."The rise of such a minuscule militancy can be rooted out very soon," said Dhaka resident Mohammad Nizam Uddin Jitu after participating in Eid prayers on Thursday at the Baitul Mukarram National Mosque in the capital."The people of this country are united," he said. "The people of this country are peace loving. The people of this country never support militancy."