* H1 pretax profit 184.5 mln pounds vs 192 mln loss yr ago
* Underwriting profit 153.8 mln vs 203.8 million loss
LONDON, Aug 20 (Reuters) - Lloyd's of London insurer Amlin PLC swung back to profit in the first half of 2012, helped by a sharp drop in catastrophe-related claims and higher premiums.
Amlin booked pretax profit of 184.5 million pounds ($289.2 million) in the six months to end-June on Monday compared with a pretax loss of 192 million pounds a year earlier.
Its shares rose after the results announcement and were up 3.8 percent to 395.4 pence by 1050 GMT.
Bringing further cheer to investors, the group also said it had agreed a new five-year, unsecured 300 million pounds debt facility with its lenders, replacing a 250 million pounds loan that was due to mature in September 2013.
"This is a welcome return to profit and the strength of our underwriting result underlines the quality and diversity of our business," Chief Executive Charles Philipps said in a statement.
Global insurers suffered losses of $116 billion in 2011 after a slew of natural disasters including Japan's Tohoku earthquake led to a surge in claims.
Premiums have risen as a result and the absence of an earthquake, hurricane or flood of similar magnitude so far this year has helped stronger insurers to grab more market share at the expense of smaller rivals still grappling with last year's big payouts.
Amlin reported an underwriting profit of 153.8 million pounds, compared with a loss of 203.8 million pounds a year ago.
The group raised its half-year dividend by 4.2 percent to 7.5 pence per share.