UPDATE 2-New efficiency drive, slower sales growth weigh on Securitas

* Q4 EBITA 1.5 bln SEK vs consensus 1.4 bln

* Q4 organic sales growth 5 pct vs consensus 6 pct

* Proposes 4.40 SEK/share dividend vs consensus 4.47 SEK

* New investments, savings programmes to squeeze free cash flow (Adds management, analyst comment, updates shares)

STOCKHOLM, Feb 7 (Reuters) - Shares in Securitas fell on Thursday after the group said it would invest heavily in coming years and reported slower-than-expected organic sales growth for the fourth quarter.

The world’s biggest security services group by revenue announced late on Wednesday programmes to modernise its IT platform, reduce costs and boost margins in North America, and said it was considering a similar programme for its European operations.

The initiatives see CEO Magnus Ahlqvist, who took over the role in March 2018, stamping his mark on the company following a strategy review, but analysts were cautious.

“We believe this will downgrade 2019-2020 free cash flow estimates by around 25 percent and spark debate over earnings quality,” analysts at Jefferies said in a note.

The rival of Britain’s G4S said market momentum was strong throughout 2018 and it had gained market share.

However organic sales growth slowed in the final quarter, to 5 percent from 6 percent a year ago, as growth slowed in both North America and Europe. Analysts polled by Reuters had forecast 6 percent growth.

Shares in Securitas, whose services range from manned guarding and alarm surveillance to airport security, were down 5 percent at 1140 GMT, erasing their gains this year.

Operating profit before amortisation grew slightly more than expected in the quarter, helped by strong profit growth in North America, to 1.5 billion crowns ($161 mln) from 1.3 billion.

The Swedish group however proposed a lower-than-expected dividend of 4.40 crowns per share.

Chief Financial Officer Bart Adam told analysts on a conference call that half of the 1.2 billion crowns in costs and investments related to the new programmes would be booked in 2019, and the rest in 2020.

Ahlqvist told Reuters he saw the North American market growing around 4 percent in 2019, and the European market by between 2 and 3 percent.

$1 = 9.2282 Swedish crowns Reporting by Anna Ringstrom; editing by Niklas Pollard, Susan Fenton and Kirsten Donovan