Barack Obama says U.S. to investigate if Boston bombings suspects had help

U.S. President Barack Obama pledged on Friday that the United States will find out whether the two ethnic Chechen brothers suspected of carrying out the Boston Marathon bombings received help, and he pleaded for Americans not to rush to judgment, Reuters reported.

Obama appeared in the White House briefing room after police arrested the lone surviving suspect in the Boston suburb of Watertown, ending a dramatic manhunt. The other suspect was killed in a shootout overnight with police.

The U.S. leader watched the fast-paced developments on television in the White House residence, then returned to the Oval Office where he was briefed by FBI Director Robert Mueller. Relief swept the White House at the news of Dzhokhar Tsarnaev's arrest but there was no sign of a celebration.

The president, looking somber and gripping the podium, said Americans are in debt to the people of Boston and Massachusetts for their resilience in responding to the twin blasts that killed three people and injured 176 others on Monday and enduring a wrenching week.

"We will determine what happened. We will investigate any association that these terrorists may have had and will continue to do whatever we have to do to keep our people safe," Obama said.

In urging Americans to show tolerance, Obama may have been referring to the surviving suspect who is known to have posted links to Islamic websites calling for Chechen independence.

Obama appealed for Americans to avoid a rush to judgment, saying people should stay true to the "unity and diversity that makes us strong."

"That's why we have courts. That's why we take care not to rush to judgment, not about the motivations of these individuals, certainly not about entire groups of people ... We welcome people from all around the world, people of every faith, every ethnicity," he said.

Obama also attended a wrenching inter-faith service for the victims of the bombings in Boston on Thursday.

"All in all, this has been a tough week," he said. "But we've seen the character of our country once more."