Eight people were killed and more than 50 were wounded on Friday morning when suicide bombers who checked in as guests smuggled explosives into American luxury hotels in Indonesia's capital and set off a pair of heavy blasts, investigators said. The near-simultaneous bombings ended a four-year lull in terror attacks in the world's most populous Muslim nation. At least 18 foreigners were among the dead and wounded. The blasts at the J.W. Marriott and Ritz-Carlton hotels, located side-by-side in an upscale business district in Jakarta, blew out windows and scattered debris and glass across the street, kicking up a thick plume of smoke. Facades of both hotels were reduced to twisted metal. An Associated Press reporter at the scene saw bodies being shuttled away in police trucks. Alex Asmasubrata, who was jogging nearby, said he walked into the Marriott before emergency services arrived and "there were bodies on the ground, one of them had no stomach," he said. "It was terrible." Two Australians and a New Zealander were believed to have been killed, but there was confusion about the exact number of victims. "I have grave concerns for three Australians following the terrorist bombings in Jakarta earlier today," Australian Prime Minister Kevin Rudd told reporters late Friday. "One of these Australians is an Australian Embassy official. These figures may be the subject of further change." An Australian think tank, the Strategic Policy Institute, predicted the Southeast Asian terrorist group Jemaah Islamiyah might launch new attacks just a day before Friday's deadly strike. A paper released Thursday said tensions in the group's leadership and the release of former members from prison "raise the possibility that splinter factions might now seek to re-energize the movement through violent attacks." Indonesian President Susilo Bambang Yudhoyono said the attack was carried out by a "terrorist group" and vowed to arrest the perpetrators. He also suggested a possible link to the national election last week that is expected to hand him another five-year term as president, but he provided no details. Suspicion will fall on the Southeast Asian Islamist militant group Jemaah Islamiyah or its allies. The network is blamed for past attacks in Indonesia, including a 2003 bombing at the Marriott when 12 people died. "Those who carried out this attack and those who planned it will be arrested and tried according to the law," a somber-looking Yudhoyono told a news conference. The Manchester United football team canceled a planned visit to Indonesia. The team had been scheduled to stay at the Ritz on Saturday and Sunday nights for a friendly match against the Indonesian All Stars, the Indonesian Football association said. Jakarta police chief Maj. Gen. Wahyono said two suicide bombers carried out the attacks at the hotels. The suspects of the Marriott bombing stayed on the 18th floor, where un-detonated explosives were found after Friday's twin explosions. "There were several perpetrators," he told reporters. "They were disguised as guests and stayed in room 1808." U.S. Secretary of State Hillary Rodham Clinton condemned the bombings as reflecting "the viciousness of violent extremists" and said they "remind us that the threat of terrorism remains very real." She said the United States was prepared to provide assistance if requested by the Indonesian government. The European Union condemned the blasts as "brutal." The Marriott was hit first, followed by the blast at the Ritz two minutes later. Security Minister Widodo Adi Sucipto told reporters at the scene the hotel blasts happened at 7:45 a.m. and 7:47 a.m. (0045 GMT, 8:45 p.m. EDT) and that "high explosives were used." He said eight people were killed and 50 wounded. Anti-terrorist forces with automatic weapons were rushed to the site, and authorities blocked access to the hotels in a district also home to foreign embassies. "This destroys our conducive situation," Sucipto said, referring to the nearly four years since a major terrorist attack in Indonesia - a triple suicide bombing at restaurants at the resort island of Bali that killed 20 people. The security minister and police said a New Zealander was among those killed, and that 17 other foreigners were among the wounded, including nationals from Australia, Canada, Hong Kong, India, Italy, the Netherlands, Norway, South Korea the US and Britain. The dead New Zealander was identified by his employer as Timothy David Mackay, 62, who worked for cement products manufacturer PT Holcim Indonesia. He was reportedly attending a business meeting at the Marriott Hotel when the explosions occurred. Noel Clay, a US State Department spokesman in Washington, said that several American citizens were among the injured. Three Americans were listed as patients at the Metropolitan Medical Center hospital. There was no immediate claim of responsibility for the attacks, but terrorism analyst Rohan Gunaratna said the likely perpetrators were from the al-Qaida-linked Jemaah Islamiyah. "The only group with the intention and capability to mount attacks upon Western targets is Jemaah Islamiyah. I have no doubt Jemaah Islamiyah was responsible for this attack," he said. There has been a massive crackdown in recent years by anti-terrorist officials in Indonesia, a predominantly Muslim nation of 235 million, but Gunaratna said the group was "still a very capable terrorist organization." Police have detained most of the key figures in the Indonesia-based Jemaah Islamiyah and rounded up hundreds of other sympathizers and lesser figures. But Gunaratna said radical ideologues sympathetic to the group were still able to preach extremism in Indonesia, helping provide an infrastructure that could support terrorism. In October 2002 two Bali nightclubs were attacked killing 202 people, many of them foreign tourists. Jemaah Islamiyah was accused of responsibility.