BERLIN - The German government on Monday defended its export to Israel of submarines capable of carrying nuclear warheads, saying the delivery is no more than a continuity with previous administrations.

"Delivery of those submarines was definitely without armament, and the German government is not involved with any sort of speculation about the any sort of weaponry equipment in the later stage," said German Chancellor Angela Merkel's spokesman Steffen Seibert.

He said the deal was "in the continuity of their predecessor governments."

German news weekly Der Spiegel revealed on Monday that Israel had the submarines supplied and largely financed by Germany equipped with nuclear-tipped cruise missiles, stirring controversies on the morality and legality of German submarines being used as part of an Israeli atomic arsenal.

According to the report, the German government was not totally unaware of Israel arming the nuclear warheads onto the Dolphin-class vessels, which were sold to Israel at a discount price, with the German government paying some of the cost.

German opposition Social Democrats has demanded a responsive explanation on whether the federal government knew if the submarines delivered by Germany can be potentially equipped with nuclear warheads.

Germany is one of Israel's staunchest allies but has recently criticized Israel Prime Minister Benjamin Netanyahu's pro-settlement policies in the West Bank and the annexed east Jerusalem as undermining peace efforts with the Palestinians.

According to the Der Spiegel report, the German government had hoped to see Israeli concessions on settlements on Palestinian land and approval for the completion of a sewage treatment plant in the Gaza Strip in exchange for the delivery of the submarines.