Israel on Wednesday intercepted a boat carrying women activists seeking to break the country's decade-long blockade of the Gaza Strip, saying it was boarded without incident and being taken ashore.

The navy said it had redirected the sailboat in order to prevent a "breach of the lawful maritime blockade" of the Palestinian enclave "in accordance with government directives and after exhausting all diplomatic channels".

The Zaytouna-Oliva set sail from Barcelona in September with 13 women of various nationalities aboard, including 1976 Nobel Peace Prize winner Mairead Maguire of Northern Ireland.

Dubbed "Women's Boat to Gaza", it is part of the wider Freedom Flotilla Coalition that consists of pro-Palestinian boats that regularly seek to go to Gaza to try to break the blockade.

One such operation turned to tragedy in 2010 when Israeli commandos killed 10 Turkish activists in a raid on a flotilla.

In Wednesday's operation, the Israeli navy said it intercepted the sailboat after advising it "numerous times to change course prior to the action".

It said its forces had boarded and searched the sailboat, describing the operation as "uneventful".

Organisers said they had lost communication with the activists, but it is believed that the sailboat was taken to the Israeli port of Ashdod.

It was boarded around 35 nautical miles from the coast, Israeli public radio reported, citing a navy officer.

"Following their refusal, the navy visited and searched the vessel in international waters in order to prevent their intended breach of the lawful maritime blockade of the Gaza Strip."

Hamas denounced the move as "state terrorism".

Saeb Erekat, secretary general of the Palestine Liberation Organisation, also condemned the interception of the boat.

"We strongly condemn the Israeli aggression against the international flotilla that tried to break the illegal siege imposed by Israel on 1.8 million inhabitants of the Gaza Strip," he said in a statement calling for their release.

- Flare-up of violence -

Gazans had planned to celebrate the arrival of the boat, with some taking to the water in boats bearing Palestinian flags, hoping to escort it into port.

Israel and Palestinian militants in Gaza have fought three wars since 2008.

Israel maintains a blockade to keep material it believes could be used for military purposes from entering the impoverished enclave of 1.9 million people.

UN officials have called for the blockade to be lifted, saying conditions are deteriorating in Gaza.

Earlier on Wednesday, Israel's military struck several Hamas positions in the Gaza Strip after a rocket launched from the Palestinian enclave hit the nearby Israeli city of Sderot, with no casualties reported on either side.

A small Salafist group -- followers of an ultra-conservative brand of Sunni Islam who oppose Hamas -- claimed responsibility for the attack.

Israel holds Hamas responsible for all such rocket fire and often responds with air and tank strikes, but recent responses have been stronger than in the past.

That has led some analysts to question whether the change is the result of a new policy by hardline Defence Minister Avigdor Lieberman, who took office in May.

In August, Israel carried out dozens of retaliatory strikes after a rocket hit Sderot, a far larger response than usual.

Israeli media reported that attack was the first time downtown Sderot had been struck by a rocket from Gaza since the last war in 2014.

The 2014 conflict was the most devastating of the three, killing 2,251 Palestinians and leaving 100,000 homeless.

Seventy-three Israelis, most of them soldiers, died in the conflict.

A delegation from the International Criminal Court is visiting Israel and the Palestinian territories this week, its chief prosecutor said Wednesday, against the backdrop of a probe into the last Gaza war.