CAIRO (AP) — An international aid group said Wednesday that closures aimed at containing the coronavirus pandemic are preventing it from reaching 300,000 people in conflict zones across the Middle East, as the virus arrived in war-torn Libya and case counts rose in Syria and the Gaza Strip, among the world's most vulnerable places.

The Norwegian Refugee Council said it was unable to reach people in Syria, Yemen and the Gaza Strip, where authorities have imposed strict measures to halt the spread of the virus. All have fragile health care systems that could be overwhelmed by an outbreak, and only Yemen has yet to report any cases.

“While governments are taking tough and much-needed measures to prevent the spread of coronavirus, millions of refugees and displaced people still depend on humanitarian assistance,” said Jan Egeland, head of the aid group.

In northwestern Syria, hundreds of thousands of people are crammed into unsanitary tent camps, sheltering from the government offensive on the war-torn country's last rebel stronghold. On Wednesday, the U.S. urged the Syrian government to halt its campaign so those displaced can access humanitarian aid. The U.S. also urged the Assad government to release thousands of civilians arbitrarily detained in crowded jails who are especially vulnerable to the virus. On Wednesday, Syria's tally of cases rose to five and testing began after weeks of obstacles in the rebel-held province.

The crowded Gaza Strip reported seven new coronavirus late Wednesday among security workers, raising the total to nine and stoking concerns about the capacity of its weakened health system to manage coronavirus patients. Gaza has been under Israeli-Egyptian blockade since the Hamas militant group took power in 2007.

For most people, the new coronavirus causes mild or moderate symptoms that clear up in two weeks. For some, especially older adults and people with existing health problems, it can cause more severe illness. The virus is highly contagious and can be spread by those showing no symptoms.

Countries across the Middle East have imposed sweeping measures to prevent its spread, including closing their borders, canceling flights and in some cases imposing round-the-clock curfews.

In Syria, an open-ended nightly curfew took effect Wednesday at 6 p.m. local time (1600 GMT). State TV showed police patrolling the empty streets of Damascus and other main cities.

The Israeli government Wednesday approved new restrictions, including the closure of all synagogues. Many in Israel's insular ultra-Orthodox communities have defied restrictions on public gatherings, fueling tension with authorities.

Twenty-nine percent of those who contracted the virus in Israel were infected in a synagogue or a yeshiva, according to an analysis by the National Information and Knowledge Center for the Fight Against the Coronavirus, which has been advising the Health Ministry.

The new restrictions in Israel will bar most people from venturing more that 100 meters (yards) from their homes. More than 2,369 Israelis have been infected, with 39 in serious condition. Five elderly Israelis with pre-existing medical conditions have died. In a televised address, Israeli Prime Minister Benjamin Netanyahu urged citizens to obey the stringent guidelines and warned of the need for a total lockdown if the outbreak doesn't slow.

The Palestinian Authority, which governs parts of the Israeli-occupied West Bank, has ordered a full lockdown and halted travel between cities, towns and villages. Sixty-two cases have been reported in the West Bank along with the nine in Gaza. A 60-year-old woman became the West Bank's first fatality Wednesday. She was infected by her son, who caught the virus while working in Israel, according to the Palestinian Authority.

At least 3,000 workers came home to the West Bank on Wednesday, said Shahir Saed, head of the workers union, after the Palestinian leadership ordered all 65,000 Palestinian workers to return to the West Bank from Israel. Wages in Israel are much higher than in the Palestinian territories, where decades of Israeli military rule has hindered economic development.

In Libya, authorities tracked down and quarantined dozens of people who had come into contact with the country's first confirmed case, a 73-year-old man who entered from neighboring Tunisia on March 5 after traveling to Saudi Arabia. Health officials said he was in stable condition.

Libya has been mired in chaos since the 2011 uprising that overthrew and killed longtime dictator Moammar Gadhafi. It is governed by rival authorities based in Tripoli and eastern Libya whose forces have been battling over the capital for nearly a year. The capital's suburbs came under heavy fire even as the United Nations appealed for a truce so authorities could focus on the pandemic.

Meanwhile, the eastern city of Benghazi began a two-week lockdown Wednesday, although authorities have allowed residents to buy food and medicine for two hours each morning.

Streets in Egypt, the Arab world's most populous country, emptied Wednesday at 7 p.m. as a nationwide nighttime curfew took effect. President Abdel Fattah el-Sissi appealed to citizens on social media to stay inside and “preserve our safety.” Egypt has confirmed 456 cases and 22 fatalities, including two senior military officers who were involved in efforts to disinfect public places.

Iran is battling the worst outbreak in the region, with over 27,000 confirmed cases and a death toll of at least 2,077. Authorities have advised people to stay at home but have not imposed the kinds of lockdowns seen elsewhere. State television aired footage of people thronging the streets Monday night, ignoring social-distancing warnings. President Hassan Rouhani imposed new restrictions on parks, saying he was left with “no other choice."

War-ravaged Afghanistan imposed a lockdown on its western Herat province, which borders Iran and where the largest number of cases has been detected. Afghan authorities have reported 76 cases and two deaths. The NATO-led coalition in Afghanistan has reported four cases among soldiers who recently arrived in Kabul.

Saudi Arabia, meanwhile, expanded its curfew hours in the cities of Mecca and Medina, home to Islam's holiest sites, as well as the capital, Riyadh. Residents now must remain inside their homes from 3 p.m. to 6 a.m. The kingdom, which has reported 900 cases, also banned travel between three governorates.

As community transmission appears to take off in Pakistan, which has confirmed 1,000 cases and seven deaths, the country halted all domestic passenger flights beginning Thursday.

Abu Dhabi's Etihad carrier, one of the biggest in the Middle East, said it has had to cut salaries by 25-50% due to the grounding of its passenger flights.

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Associated Press writer Samy Magdy reported this story in Cairo and AP writer Joseph Krauss reported from Jerusalem. AP writers Aron Heller in Jerusalem; Munir Ahmed in Islamabad; Jon Gambrell and Aya Batrawy in Dubai, United Arab Emirates; Jan M. Olsen in Copenhagen, Denmark; Mohammed Daraghmeh in Ramallah, West Bank; Nasser Karimi in Tehran, Iran; and Tameem Akhgar in Kabul, Afghanistan, contributed to this report.

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The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.