By Alan Silverleib, CNN Congressional Producer

Washington (CNN) - Partisan tempers flared at a Senate immigration hearing on Monday as top Democrats accused opponents of comprehensive reform legislation of using last week's Boston Marathon bombings to slow or even derail the bill.

"Last week, opponents of comprehensive immigration reform began to exploit the Boston marathon bombing," said Senate Judiciary Committee Chairman Patrick Leahy, D-Vermont.

"I urge restraint in that regard. ... Let no one be so cruel as to try to use the heinous attacks of these two young men last week to derail the dreams and futures of millions of hard-working people," Leahy added.

He said the bill crafted by the bipartisan "Gang of Eight" would "serve to strengthen our national security by allowing us to focus our border security and enforcement efforts against those who would do us harm."

"A nation as strong as ours can welcome the oppressed and persecuted without making compromises in our security," he said. "We are capable of vigilance in our pursuit of these values, and we have seen the tremendous work that the local law enforcement as well as the federal law enforcement have done in the Boston area, and I am so proud of them."