Democrats in the US Senate have held the floor for nearly 15 hours through the night to demand a vote on gun control after the killing of 49 people at a gay nightclub in Florida.

The marathon session ended after Republicans agreed to hold votes on measures to expand background checks and prevent people on US terrorism watch lists from buying guns, Democratic Senator Chris Murphy said early on Thursday.

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The move could break a years-long deadlock on gun control and follows demands for action after the worst mass shooting in US history.

'I'm at my wits' end'

Murphy took to the floor of the Republican-controlled senate on Wednesday morning to launch a procedural obstruction, known as a filibuster, to press colleagues to accept so-called "no-fly no-buy" legislation.

Under the measure, people on watch lists or no-fly lists would be barred from buying firearms. Omar Mateen, the Orlando gunman, had been on such a list.

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"I'm at my wits' end," said Murphy, as he began on Wednesday morning his hours-long takeover.

"I'm going to remain on this floor until we get some signal, some sign that we can come together," added the Senator of Connecticut, where a 2012 school schooting left 20 children dead.

Murphy, with support from 40 senators, including Republican Pat Toomey, spent hours discussing ways to reduce gun violence.

At 1:53 am (05:53 GMT) onThursday, he claimed victory on Twitter.

"I am proud to announce that after 14 hours on the floor, we will have a vote on closing the terror gap & universal background checks," Murphy wrote.

Obama visit

The move comes as US President Barack Obama and Vice President Joe Biden set out for Orlando, the scene of last weekend's deadly attack.

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The White House said Obama plans to make clear during his visit today that "the country stands with the people of Orlando" and "with the LGBT community in Orlando, as they grieve for their loss".

The attack was the worst mass shooting in US history. Its perpetrator Omar Mateen claimed he was acting on behalf of the Islamic State of Iraq and the Levant group (ISIL) but was also known to have frequented the club before the attack.

Source: Agencies