MOSCOW — The brazen suicide bombings in the center of Moscow confronted Prime Minister Vladimir V. Putin with a grave challenge to his record of curbing terrorism, and raised the possibility that he would respond as he had in the past, by significantly tightening control over the government.

The explosions Monday, set off by female suicide bombers in two landmark subway stations, killed at least 38 people and wounded scores of others, touching off fears that the Muslim insurgency in southern Russia, including Chechnya, was once again being brought to the country’s heart.

The attacks during the morning rush hour seemed all but designed to taunt the security services, which have been championed by Mr. Putin in the decade since he took power in Russia. The first one occurred at the Lubyanka subway station, next to the headquarters of the Federal Security Service, also known as the F.S.B., the successor agency to the Soviet-era K.G.B. that was led by Mr. Putin in the late 1990s.

Mr. Putin, the former president and still Russia’s paramount leader, has built his reputation in part on his success in bottling up the Muslim insurgency in southern Russia and preventing major terrorist attacks in the country’s population centers in recent years. If the bombings on Monday herald a renewed campaign by insurgents in major cities, then that legacy may be tarnished.

The attacks could also throw into doubt the policies of Mr. Putin’s protégé, President Dmitri A. Medvedev, who has spoken in favor of liberalizing the government, increasing political pluralism and dealing with terrorism by addressing the root causes of the insurgency.

While Mr. Medvedev has not yet put in place many major changes, Mr. Putin has generally allowed him to pursue his course. More terrorism, though, could cause Mr. Putin to shove Mr. Medvedev aside and move the security-oriented circle of advisers around Mr. Putin to the forefront.

“Putin said, ‘One thing that I definitely accomplished was this,’ and he didn’t,” said Pavel K. Baev, a Russian who is a professor at the International Peace Research Institute in Oslo.

Image Bodies and debris covered a platform at the Park Kultury subway station in Moscow after a suicide bombing on Monday. Credit... Egor Barbatunov/Associated Press

“My feeling is this is not an isolated attack, that we will see more,” Mr. Baev said. “If we are facing a situation where there is a chain of attacks, that would undercut every attempt to soften, liberalize, open up, and increase the demand for tougher measures.”

Mr. Putin on Monday limited his comments largely to vows to destroy the terrorists who organized the attacks, who have not been identified, but who the Russian authorities said they suspect came from Chechnya or neighboring regions in the Caucasus Mountains. But when he last faced a spate of such violence, in 2004, he reacted with a sweeping reorganization of the government that he said would unite the country against terrorism, but also concentrated power in the Kremlin.

He pushed through laws that eliminated the direct election of regional governors, turning them into presidential appointees, and made it all but impossible for political independents to be elected to the federal Parliament. He also increased the strength of the security services.

Boris I. Makarenko, chairman of the Center for Political Technologies in Moscow, a research organization, cautioned that it was too soon to speculate whether Mr. Putin might feel the need to clamp down. Mr. Makarenko said he believed that Mr. Putin’s reputation had not suffered badly because of terrorist attacks early in his tenure as president.

But Mr. Makarenko noted that the bombings in the Moscow subway came as Russia’s financial problems had been agitating the government. Protests have broken out in some major cities, and the opposition, while still relatively weak, has been gaining some support.

“The public has become more skeptical about the government in general in recent months, due to the government’s limited ability to tackle the effects of the economic crisis, to the inefficiency and misbehavior of the police, and other issues,” he said. “These terrorist attacks might be another piece in the efforts of those who want to go after the government.”

The subway system in Moscow is one of the world’s most extensive and well managed, and the bombings on Monday spread anxiety that is unlikely to dissipate for some time. For many people here, the day’s events recalled the tense times in the early part of the last decade when the city, including the subway, was hit with several terrorist attacks.

While the Muslim insurgency has not subsided in recent years, major attacks outside the Caucasus region had been unusual, and in April 2009, the Kremlin even announced what it described as the end of special counterterrorism operations in Chechnya.

But in November 2009, terrorists bombed a luxury passenger train that was traveling in a rural area from Moscow to St. Petersburg, killing 26 people. Last month, a Chechen rebel leader, Doku Umarov, threatened in an interview on a Web site to organize terror acts in Russian population centers.