BERLIN, July 2 (Reuters) - Islamic militants may be planning attacks aimed at influencing public opinion against Germany's Afghanistan mission ahead of a national election, a senior official said on Thursday.

Authorities have detected an increase in threatening video messages ahead of the Sept. 27 parliamentary elections, Deputy Interior Minister and former spy chief August Hanning told a news conference.

Hanning said the 2004 Madrid bombings -- when militants killed 191 people in train bombings in an attempt to influence an approaching election and pressure Spain to pull its troops from Iraq -- was a scenario on everyone's mind.

"There has been a rise in the number of video messages and they are extraordinary," Hanning said after a meeting of security officials in Berlin.

"We're also seeing more travel towards Pakistan in particular," he said. "This is disturbing, but no reason for alarmism yet."

Several militants who have carried out attacks in Europe travelled to Pakistan and Afghanistan for training at guerrilla camps, intelligence sources say.

British security services say there have been Pakistani links to almost all of the dozen major terrorism plots foiled in Britain since 2001, and to the London bombings in 2005.

Four Islamic militants on trial for planning bomb attacks on U.S. targets in Germany last year have confessed to some of the charges. They were arrested while planning attacks in 2007 that were designed to influence German public opinion on Afghanistan.

Germany has about 3,700 soldiers on a NATO mission in Afghanistan that is increasingly unpopular at home. A total of 35 German soldiers have been killed there in the last six years.

"We are the country with the third-largest number of troops in Afghanistan...making us a particular target for (militant) groups," said Hanning. The videos showed that the groups were well aware of the political situation in Germany, he added.

"When you look at the video messages, you get the impression that people are following the political situation in Germany very closely," he said, noting their aim was to force foreign troops to leave Afghanistan. "We take these threats seriously." (Reporting by Sabine Siebold and Sarah Marsh, Editing by Elizabeth Fullerton)

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