UPDATE 1-Libyan mortar shells hit Tunisia, follow refugees
* Exodus from remote Libyan region into Tunisia
* Doctor cites refugees as saying dozens killed
(Recasts, adds quotes, background)
TUNIS, April 19 (Reuters) - Four mortar shells fired from Libya fell across the border in Tunisia this week, the latest sign of worsening violence in a remote Libyan region where residents say Muammar Gaddafi's forces are fighting rebels.
Thousands of people fleeing Libya's Western Mountains -- where some towns joined a wider revolt against Gaddafi's rule in February and are now facing an onslaught by government troops -- have poured into neighbouring Tunisia in recent days.
The state news agency TAP, citing Tunisia's Defence Ministry, said the mortar shells landed in an isolated area near the southern border town of Dehiba on Monday. No one was wounded and it was unclear who fired them.
A Libyan doctor helping refugees in a camp near Dehiba said witnesses had told him that Gaddafi's forces had stepped up their bombardment of towns in the Western Mountains.
The doctor, who gave his first name as Abdelrahman, also cited them as saying that dozens of people -- both rebels and civilians -- had been killed in the last week. Continued...