WASHINGTON - US President Barack Obama on Tuesday defended the performance of law enforcement authorities including the FBI and praised the Russian side's cooperation following the Boston bombings.

Speaking at a White House news conference, Obama told reporters that all the US law enforcement officials had performed in "an exemplary fashion" after the Boston bombings took place on April 15.

Obama moved on to defend the country's national security team over reports about the alleged lack of enough intelligence sharing prior to the Boston bombings.

"But what I can say is that based on what I've seen so far, the FBI performed its duties. Department of Homeland Security did what it was supposed to be doing," said Obama.

However, the President acknowledged that the Russian intelligence services had alerted US intelligence about the older suspect in the case and the FBI had investigated him and concluded there were "no signs that he was engaging in extremist activity."

"It's not as if the FBI did nothing. They not only investigated the older brother, they interviewed the older brother," said he.

Obama stressed that one of the dangers the country now faces is "self-radicalized individuals who are already here in the United States, in some cases may not be part of any kind of network, but because of whatever warped twisted ideas they may have, may decide to carry out an attack."

"And those are, in some ways, more difficult to prevent," said he.

Obama also said the Russians had been "very cooperative" with the US authorities since the Boston Marathon bombings.

He noted that he had spoken directly to Russian President Vladimir Putin, who was committed to cooperation in investigation to the Boston bombings and counterterrorism issues.

But he acknowledged that there were still "suspicions sometimes " between the two countries' intelligence and law enforcement agencies.

Twin explosions occurred on April 15 near the finish line of the Boston Marathon, killing three people and wounding 264. The FBI identified two brothers, 26-year-old Tamerlan Tsarnaev and 19- year-old Dzhokar Tsarnaev, as suspects behind the Boston bombings. The elder brother died after a shootout with the police. Dzhokar Tsarnaev was apprehended four days after the bombings and charged last week with using a weapon of mass destruction against persons and property.

The White House news conference comes on the 100th day of the president's second-term. Obama answered a wide range of questions from foreign policy issues related to Syria to domestic issues on immigration reform and gun control, regarded as two top legislative priorities in his second-term.