Germany’s national security council approved the sale of three more nuclear-capable submarines to Israel for a combined price of some $1.3 billion, in a deal marred by controversy surrounding corruption allegations against Prime Minister Benjamin Netanyahu.

The Israeli Navy currently maintains a fleet of five state-of-the-art German underwater vessels of the Dolphin Class, which can be equipped with nuclear warheads, with a sixth due for delivery this year.

At this stage, the new submarines are not meant to expand the navy’s fleet and would not actually reach Israel for at least another decade. Rather, they would replace the military’s older submarines, which would be approaching obsolescence around the same time, the Times of Israel reported late last year.

Submarines, unmatched in their ability to hide from enemy navies, have long been a major facet of Israel’s defense policy.

Israeli subs are reportedly armed with cruise missiles topped with nuclear warheads, affording the tiny Jewish state “second strike” capabilities — although the government will not acknowledge the existence of these nuclear weapons, as part of its long-standing policy of “nuclear ambiguity.”

The approval of the deal on Friday was first reported by Der Spiegel which did not cite the source of the information.

The German paper further reported that the council decided the deal would be called off if an investigation into corruption suspicions yielded any indication of wrongdoing, according to Channel 2.

Both Israel and Germany opened separate probes into allegations Netanyahu’s personal lawyer allegedly swayed multi-billion shekel deals in favor of the German shipbuilder ThyssenKrupp he represented in Israel. The company was awarded the contracts to build the submarines.

Attorney General Avichai Mandelblit ordered the Israel Police to formally look into the affair in November 2015 after accusations surfaced that the prime minister may have been swayed to purchase the vessels by business ties David Shimron may have had with ThyssenKrupp. The purchase was opposed by parts of the defense establishment, including then Defense Minister Moshe Ya’alon.

The deal came under intense scrutiny late last year after it was revealed by Channel 10 news that Shimron also served in an advisory capacity for ThyssenKrupp.

Police were checking whether the premier himself may have sought to influence the deals due to his ties to Shimron.

The probe is known in Israel as “Case 3000” and is one of several graft investigations involving the prime minister.

Ya’alon recently testified against Netanyahu in the case, saying the PM was directly involved in negotiating the purchase of at least three submarines with German officials. Those talks were done without the involvement of Israel’s security establishment, Ya’alon reportedly said.

AFP contributed to this report