ST. PAUL — A proposal to require background checks for all Minnesota’s gun purchases ignited controversy at a Senate hearing Thursday, demonstrating what’s likely to be the biggest dividing line as the Legislature grapples with gun control measures.

Senators on the Judiciary Committee reviewed that and other proposals at a Capitol hearing that again drew large crowds largely comprised of gun control opponents. But, several weeks after the House considered a variety of gun restrictions including an assault weapons ban, the Senate narrowed the potential areas of dispute between gun control supporters and opponents.

Judiciary Committee chairman Sen. Ron Latz, DFL-St. Louis Park, reaffirmed his committee wouldn’t consider any bans on weapons or ammunition sales in the state. And the president of the Gun Owners Civil Rights Alliance, an NRA ally, said the group did not oppose Latz’s bill to toughen various legal penalties for convicted felons who go on to commit further gun crimes.

But sharp differences remained over the background check requirement. The proposal, sponsored by Sen. Bobby Joe Champion of Minneapolis, would extend government background checks beyond sales from licensed dealers, to include weapons purchases made online, at gun shows, garage sales or between two private citizens.

“All of those paths are exploited by gun traffickers, and these guns end up on our streets,” said Champion, who represents some of the city’s most crime-plagued areas. Minneapolis Mayor R.T. Rybak, who in recent weeks has jumped into the larger national debate around gun control sparked anew by December’s elementary school shootings in Connecticut, cited a 2003 fatal shooting at Hennepin County Government Center by a woman using a gun purchased at a show.