* German govt under gun over secretive Saudi tank deal
* Arms sale may violate Germany's own export laws
* Controversial deal for 200 state-of-art German tanks
BERLIN, July 5 (Reuters) - Chancellor Angela Merkel's government faces a grilling in parliament over a secret sale of tanks to Saudi Arabia that Germany's opposition argues reverses a post-war stance severely restricting arms sales abroad.
Reuters reported from Riyadh on Monday that Saudi security sources had confirmed a deal for 200 Leopard 2 tanks, fuelling a growing political debate over the arms sale after Der Spiegel magazine leaked first details about it on Sunday.
Germany has long imposed rules on its arms exporters barring them from selling weapons to countries in crisis areas as well as those with human rights problems and or engaged in armed conflicts. The Middle East, with the exception of Israel, was long considered such a taboo area of tension.
Saudi Arabia has been eager to buy German tanks for the last 30 years but was until now turned down.
Defence Minister Thomas de Maiziere called the issue a matter of national security, and declined comment.
"Meetings of the national security council are classified and they're going to stay that way," de Maiziere told reporters on Tuesday.
Opposition lawmakers said they would demand answers in a parliamentary debate on Wednesday about the news reports.
"At some point the government is going to have to give up its veil of secrecy and come clean," said Juergen Trittin, parliamentary floor leader for the opposition Greens party.
"Just try to keep it secret when you start delivering multi-tonne tanks to Saudi Arabia," Trittin added.
Selling armaments abroad is a sensitive issue in Germany due to its Nazi past, but also because of the notorious role arms makers such as Krupp played in feeding 19th and 20th century wars with exports of weapons to virtually all belligerents.
But despite its self-imposed restrictions, Germany's arms exports have doubled in the last decade and the country has moved ahead of Britain and France to become the world's third largest exporter of weapons behind the United States and Russia.
About 90,000 work in the fast-growing defence sector. The 2A7+ tanks, made by Krauss-Maffei Wegmann and Rheinmetall , are considered to be one of the best main battle tanks built anywhere in the world.
Israel has not commented on the report, adding to speculation that Germany had cleared the deal with its long-time ally in advance.
"Normally you'd expect at least Israel would object if Saudi Arabia got a delivery of tanks," said Joachim Hoerster, a member of Merkel's conservatives and expert about Arabic nations.
"That was always the case in the past and that's why no (German) arms went there before. But the geo-political situation in the Middle East has evidently changed so much that Israel has no comment on all this -- and that speaks volumes by itself."
Germany's relations with Israeli have been shaped by the memory of the Holocaust and all post-war governments have unambiguously supported the country.
In Jerusalem, an Israeli defence official declined to discuss any specific deal. But in general he said:
"I can't imagine we would be bothered by such a deal as we don't have a land border with Saudi Arabia," the official said.
Gernot Erler, deputy parliamentary floor leader for the opposition Social Democrats, said such a tank sale would be illegal.
"When reports like that aren't immediately denied, there's usually some truth to it," Erler, a former deputy foreign minister, told Deutschlandfunk radio.
"The Saudi regime is one of the most despotic in the Arab world," added senior Greens MP Christian Stroeble. "The country disregards human rights and has helped its neighbours beat back pro-democracy movements."
Even members of parliament in Merkel's centre-right coalition expressed misgivings.
Coalition sources told Reuters that at a meeting of conservative deputies in parliament late on Monday senior MPs such as Reprecht Polenz, parliament president Norbert Lammert and human rights expert Erika Steinbach criticised the deal.
Some conservative deputies expressed support, however, saying that other German allies sell tanks to Saudi Arabia and, moreover, the country is an important strategic ally.