NGO rescue ship Sea Watch 3 has been allowed to anchor off Syracuse in Sicily by the Italian coastguard, as the sea conditions have worsened.

The ship is carrying 47 migrants, which it rescued on January 19 in Libyan waters, and which since then has not been allowed to disembark them.

The coastguard said the rescue had been undertaken without the coordination of the relevant search and rescue centre.

Read: Migrant rescue ship stranded at sea again

Once the migrants were taken on board, the weather turned much worse and the ship went first towards Lampedusa and then to Sicily seeking shelter.

Italy's deputy prime minister Matteo Salvini has insisted the boat will not be allowed to dock amid a clampdown against migrant NGO rescue vessels. 

As the sea worsened, the ship was assigned to a point 2km offshore, which was considered to be a safer option for those on board. The boat is being monitored by coastguard and customs vessels.

A spokesman for the NGO on Monday told Times of Malta that while they had made contact with the Maltese and Italian authorities, both were adamant that the vessel should instead reach out to their Libyan counterparts as they were the competent rescue coordinating authority.

The spokesman said repeated efforts to contact the Libyan coast guard and other Libyan authorities in recent days had proven unsuccessful as they remained unresponsive.