Two large bomb blasts ripped through the Ritz-Carlton and JW Marriott hotels in the Indonesian capital Jakarta Friday morning, killing eight and wounding 53 in the first terror attack in the Southeast Asian nation since 2005.

No group has yet claimed responsibility, but suspicion immediately fell on regional terror network Jemaah Islamiyah and one of its master bomb makers and strategists - Noordin Mohammed Top.

President Susilo Bambang Yudhoyono said his government would step up security measures following the "inhuman" act of terror.

It wasn't immediately clear how many of the dead were foreigners. Among those killed was PT Holcim Indonesia's (SMCB.JK) Chief Executive Timothy Mackay. He was at the Marriott, a company official said, and died from his injuries in a hospital.

Police revised the death count to eight from nine Friday afternoon. Eighteen of the wounded were foreigners, police said.

The streets outside the two hotels, which are adjacent to each other in the Mega Kuningan central business district, were covered in shattered glass and debris. Smoke billowed as dazed and bloodied workers and hotel guests milled outside.

The facade of the Ritz-Carlton was blown off after an explosion in the restaurant while people were having breakfast, police said.

An unexploded bomb was later found in a room at the Marriott and was disposed of.

Jakarta police chief Wahyono told reporters the perpetrator of the JW Marriott attack had "disguised himself as a guest."

At a news conference, President Yudhoyono alleged there was a plot to prevent his re-election, calling the attackers "spreaders of death."

"Today, bombings have been perpetrated by terrorist groups. I cannot yet say whether these groups are the same ones" that have carried out attacks in the past, Yudhoyono said in a speech broadcast on local television. "This may have a wide impact on our economy, on tourism, and the business climate."

Jakarta's benchmark stock index opened down more than 2% after the blasts but recovered somewhat and closed down 0.6%.

Indonesia's Finance Minister Sri Mulyani Indrawati said the government would make efforts to minimize the attacks' impact on the local currency and wider economy.

"If the impact is significant, we will take serious steps," Mulyani said at a news conference.

Ben Sukma, chairman of Indonesia's tourism association, ASITA, admitted there would "definitely be an impact" on tourism following the strikes.

Australia has already urged citizens to reconsider the need to travel to the archipelago, as Prime Minister Kevin Rudd described the attacks as "barbaric." Singapore, meanwhile, urged citizens to be vigilant.

"We continue to receive credible information that terrorists could be planning attacks in Indonesia and that Bali remains an attractive target for terrorists," an Australian foreign ministry statement read.

Citizens from the U.S, Netherlands, India, Canada, Australia and South Korea were among the injured, reports said.

U.S. Secretary of State Hillary Clinton condemned the attacks and said Washington would help the Indonesian government if asked.

"The attacks reflect the viciousness of violent extremists, and remind us that the threat of terrorism remains very real," Clinton said in a statement issued from Prague as her plane stopped for refueling en route to India.

The European Union presidency also issued a condemnation.

"We stand in sympathy and solidarity with the Indonesian government and the Indonesian people in this most difficult time," it said in a statement.

Indonesia, the world's most populous Muslim nation, hasn't suffered a major terrorist attack since the 2005 restaurant bombings on the resort island of Bali. The JW Marriott was the target of an earlier bombing in 2003 that killed 12.

That blast was blamed on regional terror group Jemaah Islamiyah, as was the 2002 Bali nightclub bombings that killed 202 people.

Jemaah Islamiyah is largely believed to have been weakened since it carried out a series of high-profile terror strikes that began in Bali in 2002.

Analysts believe the network is weakened after a number of its leaders were arrested and some prosecuted. Three of the 2002 Bali bombers have also been executed.

But one JI mastermind - Noordin Mohammed Top, a Malaysian - is still on the run and widely believed to be in Indonesia. He has been described by the U.S. government as one of the "most dangerous members" of Jemaah Islamiyah.

"He is believed to be a top recruiter, strategist, and fundraiser," Noordin's description on the U.S. "Rewards for Justice" Web site read.

"He is a charismatic leader and a recruiter, and has proven to be innovative and single-minded in his desire to implement the Al Qaeda line and target Western interests," it said.

Also Friday, English soccer team Manchester United - who were supposed to stay at the Ritz-Carlton - said they would cancel the Jakarta leg of their Asian tour.

-By Jakarta Bureau, Dow Jones Newswires; 62-21 39831277; I-Made.Sentana@dowjones.com