Frontline said it had raised its all-share offer to 0.80 Frontline share per DHT share from an initial 0.725 but that DHT had again rejected the offer.
"As DHT's largest shareholder we are surprised that DHT's board has declined our repeated attempts to discuss a business combination that we believe is clearly in the best interest of all shareholders," Frontline CEO Robert Hvide Macleod said in a statement.
He decline to comment further when contacted by Reuters. Frontline holds a 16 percent stake in DHT.
Last month Frontline, controlled by shipping tycoon John Fredriksen, made a non-binding, all-share offer to acquire DHT to create the largest private tanker firm in the world.
That initial offer was unanimously rejected by DHT's board.
In the fourth quarter, Frontline reported an operating profit of $17.8 million, below the $35 million expected by analysts polled by Reuters and down from $77 million a year earlier.
In its market outlook, Frontline reiterated that it expected freight rates to remain under pressure as more new tankers enter the market but that the market would begin to tighten in 2018.
Shares in Frontline were up 0.53 percent at 0801 GMT while the Oslo benchmark index .OSEBX was up 0.12 percent.
Editing by Jason Neely