Foreign Minister Mohammad Javad Zarif said on Sunday talks with world powers this week are unlikely to result in a comprehensive accord on Iran's controversial nuclear drive.

"This round of talks will be more serious than previous ones," Zarif said in remarks reported by the official IRNA news agency.

The U.N.-Arab League envoy for Syria, Lakhdar Brahimi, arrived in Tehran on Sunday for talks on the Syria crisis with top Iranian officials, media reports said.

The Fars news agency said he would meet President Hassan Rouhani and Foreign Minister Mohammad Javad Zarif and other officials during his three-day visit.

Iran has to take some "tough decisions" as world powers seek to hammer out a nuclear deal, U.S. Secretary of State John Kerry said Thursday with negotiations due to resume next week.

His comments came as he was grilled by U.S. lawmakers over the talks between Iran and the so-called P5+1 group, which are due to start up again in Vienna on Monday.

Iranian President Hassan Rouhani sought Thursday to mend fences between his mainly-Shiite country and Sunni-dominated Gulf monarchies distrustful of Iran's nuclear ambitions and its support of the Syrian regime.

Rouhani, winding up a two-day visit to Oman, said the Islamic republic offered "a hand of fraternity to all the countries of the region."

U.N. Secretary General Ban Ki-moon harshly criticized Iran Wednesday for doing too little to improve its human rights situation, noting more executions, the detention of regime opponents and discrimination against women.

The United Nations' concerns about rights violations in the Islamic republic include "amputations, flogging, increased application of the death penalty, arbitrary detention and unfair trials," Ban said in a new report.

Britain will stand firm against attempts to delegitimize or boycott Israel, Prime Minister David Cameron told MPs in Jerusalem on Wednesday, shortly before Palestinian militants fired at least 25 rockets at the Jewish state.

Speaking at the outset of a two-day visit to Israel and the Palestinian territories, Cameron gave a 20-minute address to the parliament, pledging "rock solid" support for Israel's security and expressing "deep skepticism" over Iran's nuclear intentions in a speech which checked all the right boxes and won him sustained applause.

Iranian newspapers on Monday welcomed European Union foreign policy chief Catherine Ashton's weekend visit to Tehran although her focus on human rights came under criticism.

Ashton met on Sunday with top Iranian officials, including President Hassan Rouhani and Foreign Minister Mohammad Javad Zarif.

Israel will on Monday display weaponry from an intercepted ship it says was destined for Gaza in a bid to expose the "true face of Iran" which allegedly dispatched it.

The military says it found 40 long-range M-302 rockets aboard the Panamanian-flagged Klos-C it intercepted in the Red Sea last week, as well as 181 122mm mortar shells and approximately 400,000 7.62-caliber rounds.

The Israeli army was on Sunday unloading a ship which it intercepted in the Red Sea allegedly transporting arms from Iran to Gaza and escorted to the port of Eilat.

An AFP correspondent said dozens of containers from the Panamanian-flagged Klos-C were being unloaded and transferred on trucks to a nearby navy base.

EU foreign policy chief Catherine Ashton, who coordinates nuclear talks between Iran and world powers, arrived in Tehran on Saturday, media reported.

Her visit comes amid a recent thaw in Iran's strained relations with the West following last year's election of moderate Iranian President Hassan Rouhani and over its controversial nuclear program.