Four Swedes have been transferred to a prison in Beersheba, while five other Swedes have been given an ultimatum by Israel, the Swedish foreign ministry said, following Israel's deadly storming of the Ship to Gaza convoy of ships.

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Daily Dagens Nyheter said late Monday that famous writer Henning Mankell, medical doctor Viktoria Strand, artist Dror Feiler, Saman Ali and Green Party MP Mehmet Kaplan have been given an ultimatum by Israel: sign a paper and be deported, or be taken to an Israeli court.

A total of 50 people are said to have been brought to the Ela prison in Beersheba. The four imprisoned Swedes are: Ulf Carmesund, Henry Ascher, Kimberly Soto Aguayo and Amil Sarsour.

"We won't be able to meet the jailed Swedes until tomorrow", Anders Jörle, press officer at the Foreign Office, told the newspaper.

Sweden’s Foreign Ministry Carl Bildt earlier on Monday called on the Israeli ambassador to explain the violence.

"This is a very serious situation, it will have very serious consequences," Carl Bildt told Swedish Radio said. "Therefore it is very important that we clarify facts and then we will continue with our response according to that".

Ambassador Benny Dagan told Swedish Radio News that Israel has international law on its side.

"We have the right to inspect the ships in the area, which is designated within the agreement between us and the Palestinians," Dagan said. "So once it's there we have every right to stop them, to inspect it. If they resist, we can use all kind of means to make sure that they will obey our orders."

United Nations Secretary General Ban Ki-moon said he was "shocked" by the navy assault on a convoy carrying hundreds of pro-Palestinian activists, lawmakers and journalists through international waters towards besieged Gaza.