MOSCOW - President Dmitry Medvedev, describing Russia as welcoming investment and global engagement, told world economic leaders Wednesday evening that this week's suicide bombing at a busy Moscow airport could have happened anywhere and suggested that his country is weary of being lectured about democracy.

Medvedev, giving the keynote speech at the World Economic Forum in Davos, Switzerland, had planned to use his remarks at the annual gathering to reassure business leaders about the wisdom of investing in Russia, despite criticisms about an arbitrary legal system and risky business climate. But Monday's attack, which killed 35 people and injured more than 100, forced him to address terrorism as well.

The identity of the bomber has not yet been established, but Prime Minister Vladimir Putin said earlier Wednesday that preliminary evidence ruled out a connection to Chechnya, where Russia fought two civil wars before the region was brought under the brutal control of a leader loyal to Moscow. The Chechnya dispute has been the source of previous terrorist attacks.

At the same time, the Interfax news agency reported that investigators had produced a composite sketch of a bomber who was from the North Caucasus region, which could refer to republics bordering Chechnya. Other reports suggested that a female bomber was also involved.

Medvedev delayed his trip to Davos because of Monday's attack. He decided to return home early after his speech, which was preceded by a moment of silence for the bombing victims.

"They expected their act would bring Russia to its knees," he said of the attackers. "They expected and hoped that the president of Russia would not come here to attend this forum, among other things. But they miscalculated."

No nation in the world is immune to terrorism, he said. "The reality is such that terrorist acts like the one that just happened in Russia can happen anywhere."

Before leaving for Switzerland, Medvedev fired the official in charge of the Moscow transportation police, and the three police officials in charge of security at Domodedovo Airport were dismissed.

"Those who did not work properly must be punished," Medvedev said. "All the officials responsible for organizing [security] must be brought to their senses."

Russians observed a national day of mourning for the victims of the explosion, some of them passengers entering the arrivals hall, others drivers and friends waiting to meet them.

One Briton, two Tajiks, two Austrians, one Uzbek, one German and one Ukrainian were reported among the victims.

Beyond the bombing, in his Davos speech Medvedev presented a picture of a country eager to embrace the wider world. "Our task is to turn Russia into a more attractive place for the best minds of the world," he said, adding that it is improving its infrastructure, shaping laws supportive of business and eager to join the World Trade Organization. But he suggested that there are limits.

"Russia is rebuked for the lack of democracy, authoritarian tendencies and the weakness of the judicial system," he said. "Today we are the way we are. Russia indeed faces many difficulties in building the rule of law.

"All of our decision-makers are not immune to ordinary mistakes. But one thing should be understood. We are moving ahead in fighting corruption and modernizing the judicial system, although we have not yet scored tremendous success. But we will persevere. We are ready to receive friendly advice, but we do not need lecturing."

Medvedev did not mention the case of former oil tycoon Mikhail Khodorkovsky, who was tried for a second time last year on charges widely considered politically motivated, and sentenced to a term that would keep him imprisoned for six more years.

When asked about Khodorkovsky in a Bloomberg Television interview, Medvedev said that "an investor must obey the law," or "otherwise he may get a prison term as Khodorkovsky or [Bernard] Madoff" did. His words were reminiscent of hard-line remarks by Putin, and he did not dismiss the notion of a third trial for Khodorkovsky.

"No one will have any doubts that the prosecution has the right to bring additional charges against persons who are in prison, no matter how this is perceived," Medvedev said.

Earlier Wednesday, Russian officials met with investors in an attempt to interest them in a $15 billion project to build five ski resorts in the North Caucasus, an area the State Department warns Americans against visiting. The project is called Peak 5642; Mount Elbrus, one of the sites, is 5,642 meters (about 18,500 feet) tall.

"There are plenty of examples from around the world of how tourism can successfully be developed in areas with high security risks. Look at Turkey, Egypt and Israel," said Akhmed Bilalov, vice president of the Russian Olympic Committee and chairman of the project. "We are also offering very attractive guarantees on investments."