Dhaka - Bangladesh forces stormed a restaurant where heavily armed militants held dozens of people hostage for 10 hours Saturday morning, triggering explosions and finding at least five bodies lying in pools of blood and killing six gunmen. Japan's government said that 12 people were rescued.The Islamic State group claimed responsibility for the attack on the Holey Artisan Bakery in Dhaka's Gulshan area, according to the SITE Intelligence Group, which monitors jihadis activity online. At least 35 people, including about 20 foreigners, were trapped inside the restaurant, said kitchen staffer Sumon Reza, who was among more than 10 people who managed to run to the rooftop and escape when the militants moved in Friday night.With the sound of gunfire and explosions, local TV stations reported that the rescue operation began at 07:40. It included army personnel with automatic weapons and at least seven armoured vehicles. Several ambulances were on standby.Local media reported that an Argentine and two Bangladeshis were rescued from the restaurant early Saturday, but details about their condition were not immediately available.Commandos storming the restaurant discovered five bodies lying in blood, a police official who was not identified told Channel 24 TV station.In Tokyo, Deputy Chief Cabinet Secretary Koichi Hagiuda said that 12 people were rescued in the raid, including two foreigners, but he couldn't say if they were Japanese. His information was based on Dhaka police.A news agency affiliated with the Islamic Group claimed that 24 people had been killed and 40 wounded, including foreigners, according to SITE. The figures could not be independently confirmed.The Amaq news agency also posted photos purportedly showing the bodies of hostages. The authenticity of the pictures could not be confirmed either.The attack marks an escalation in the growing drumbeat of militant violence to hit the traditionally moderate Muslim-majority nation in the past three years, but with increasing frequency in recent months. Most attacks have been by machete-wielding men singling out individual activists, foreigners and religious minorities.Bangladesh did not immediately respond to the claim of responsibility by ISIS, but in the past have denied that the extremist group has a presence in the country. The US State Department said it had seen the ISIS claim, but could not confirm its authenticity.Internet blockedThe attackers "have not responded to authorities' calls for negotiation," said a member of the elite anti-crime force, Rapid Action Battalion, identifying himself as Lt Col Masood, during an interview with the Indian TV channel Times Now.He said that the security cordon would prevent any of the attackers from escaping. Authorities also ordered internet services to be blocked across the country, according to internet service provider Aamra.Police said the two officers died at a hospital after being wounded in the initial gunfire with as many as nine attackers, who also hurled bombs. Ten of the 26 wounded were listed in critical condition, six of whom were on life support, according to hospital staff, who said the injuries ranged from broken bones to gunshot wounds. Only one civilian was among the wounded.Reza said the attackers chanted "Allahu Akbar" (God is Great) as they launched the attack around 21:20 on Friday, initially opening fire with blanks. A huge contingent of security forces cordoned off the area around the bakery.The nationalities of the hostages were not immediately clear. On Saturday, Japan's top government spokesman Yoshihide Suga said at a hastily called news conference in Tokyo that the government is trying to confirm that Japanese were among the hostages. Prime Minister Shinzo Abe told reporters that saving lives is the top priority."Some derailed youths have entered the restaurant and launched the attack," Benazir Ahmed said. "We have talked to some of the people who fled the restaurant after the attack. We want to resolve this peacefully. We are trying to talk to the attackers, we want to listen to them about what they want.""Our first priority is to save the lives of the people trapped inside," Ahmed said. He would not say how many people were being held hostage.Among the hostages was a businessman and his wife and two children, according to his uncle Anwarul Karim."My nephew Hasnat Karim called me and said he was inside with his family. He told me, 'Please save us, please!' And he hung up," he said. "We do not know what is going on there."Religious extremistsIn Washington, a White House official said President Barack Obama was briefed on the attack by his chief counter-terrorism adviser Lisa Monaco. The president asked to be kept informed as the situation develops, said the official, who was not authorized to speak publicly about the president's meetings.State Department spokesperson John Kirby says the US is in contact with the Bangladesh government and has offered its assistance to bring those responsible to justice.He said all official American personnel are accounted for with no injuries reported, and the department is working with local authorities to determine if any US citizens and locally-employed staff were affected.The spree of recent attacks in Bangladesh have raised fears that religious extremists are gaining a foothold in the country, despite its traditions of secularism and tolerance.About two dozen atheist writers, publishers, members of religious minorities, social activists and foreign aid workers have been slain since 2013. On Friday, a Hindu temple worker was hacked to death by at least three assailants in southwest Bangladesh. IS and and al-Qaeda affiliates have claimed responsibility for many of the attacks.Prime Minister Sheikh Hasina's government has cracked down on domestic radical Islamists. It has accused local terrorists and opposition political parties - especially the main opposition Bangladesh Nationalist Party and its Islamist ally Jamaat-e-Islami - of orchestrating the violence in order to destabilize the nation, which both parties deny.