Two large bomb blasts hit the Ritz-Carlton and JW Marriott hotels in the Indonesian capital on Friday, killing nine and wounding nearly 50 in the first terror attack in the Southeast Asian nation since 2005.

Suspicion immediately fell on regional terror network Jemaah Islamiyah and one of its master bombmakers and strategists - Noordin Mohammed Top.

President Susilo Bambang Yudhoyono meanwhile, said his government would step up security measures following the "inhuman" act of terror. He said he didn't know which group was responsible for the attacks yet.

Several foreigners were among the dead in the twin hotel explosions early Friday morning in Jakarta. Nearly 50 people were also wounded, Agence France-Presse said.

The streets outside the two hotels, which sit adjacent to each other in the Mega Kuningan business district in central Jakarta were covered in shattered glass and debris.

White smoke billowed in the aftermath of the blast. Dazed and bloodied workers and hotel guests milled outside soon after the explosions.

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

An unexploded bomb was later found at the Marriott, the local TVOne station said. It has since been detonated.

Authorities were acting on the assumption that the bombing was carried out by Muslim extremists, said a senior counterterrorism official, the Wall Street Journal reported.

Chief security minister Widodo AS said nine people were killed and 41 wounded. He said the blasts were caused by high-level explosives.

At a news conference, President Yudhoyono alleged there was a plot to prevent his reelection, 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."

Indonesia's share market initially slumped 2.6% after the blasts, but the index came off its lows to be down 1.5% just before midday local time, as some investors opted to focus on the country's economic and political prospects.

"Global factors are still in favor of Indonesia. Pessimism over the U.S. economy is receding, encouraging global investors to reenter emerging markets, including Indonesia," said Standard Chartered economist Eric Sugandi.

Still, Ben Sukma, chairman of Indonesia's tourism association, ASITA, admitted there'll "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.

Four foreigners were killed, The Associated Press and local Metro TV said. The blasts may have come from the front and the basement of the hotels, the Antara news agency said.

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 hospital.

Shares of Holcim Indonesia (SMCB.JK) were down 3.8% shortly after the news broke of Mackay's passing.

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

The first explosion took place around 7:40 a.m. local time (0045 GMT) with the second occurring minutes later.

"I heard at least three explosions and now white smoke is billowing," a fund manager at a foreign securities company told Dow Jones Newswires by phone.

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 - Malaysian Noordin Mohammed Top - 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. They were scheduled to arrive Sunday for a sold-out game against an Indonesian selection.

The Jakarta strikes appear to be the latest luxury hotels targeted in a series of recent attacks in Asia.

More than 50 people were killed and more than 250 injured after a suicide bomber blew up an explosive-laden truck outside the Marriott in Islamabad in September last year.

In India's commercial capital Mumbai, nearly 170 people were killed after gunmen laid siege to the landmark Taj Mahal and Oberoi hotels last November. Analysts have long warned hotels were a prime target for terrorists.

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