Israel's army and Gaza militants traded heavy cross-border fire overnight, with at least 22 Palestinians killed over two days in the worst escalation of violence to hit the coastal territory in months.

Sirens in the Tel Aviv area and Israel's south warned of incoming rockets, with an AFP reporter observing launches from Gaza as Israeli officials said Egypt was working on a possible truce with the militant group Islamic Jihad.

Saudi Arabia has invited Syrian President Bashar Assad to the upcoming Arab League summit in the oil-rich kingdom, the Syrian president's office said on Wednesday. The news comes as Damascus continues to slowly return to the Arab fold, following a 12-year-period of political isolation.

Assad received the invitation days after the Arab League restored Syria's membership into the organization during a meeting in Cairo on Sunday. Syria's membership was suspended for brutally cracking down on mass protests against Assad in 2011. Since then, the uprising turned into a vicious civil war that killed nearly a half million people and displaced half of the country's pre-war population of 23 million.

Israel and Gaza militants traded cross-border fire Wednesday, renewing deadly violence a day after Israeli strikes killed 15 people in the Palestinian territory.

Smoke billowed from the densely-populated coastal territory after Israel announced it was targeting rocket launching infrastructure held by Islamic Jihad militants.

Russia on Wednesday proposed a roadmap to normalise ties between Syria and Turkey at the first meeting of their foreign ministers since the start of the Syrian civil war over a decade ago.

"Our task is to determine the general guidelines for further progress," Russian Foreign Minister Sergei Lavrov said at the meeting that also included Iran's top diplomat.

Israel's Shin Bet internal security agency is defending its use of a sophisticated surveillance tool that was used to send threatening text messages to Palestinian protesters during unrest at Jerusalem's most sensitive holy site two years ago.

A leading civil rights group has asked Israel's Supreme Court to halt the practice, saying the threatening messages exceeded the authorities of the Shin Bet. It has also noted that the messages were sent erroneously to people uninvolved in the unrest.

The United States and Britain voiced dissatisfaction Tuesday with the weekend decision by the Arab League to re-instate Syria as a member.

U.S. Secretary of State Antony Blinken and British Foreign Secretary James Cleverly said they opposed the move. But they also allowed it was up to the Arab League to determine its membership.

Saudi Arabia and Syria will reopen diplomatic missions between the two countries now that relations have improved 11 years after the facilities were closed, the two nations foreign ministries said.

The announcements came nearly a month after Syria and Saudi Arabia said they were moving toward reopening embassies and resuming airline flights. That had followed a visit by Syria's top diplomat to the kingdom, the first since Saudi Arabia cut off diplomatic relations with Syria in 2012 and a visit by Syria's foreign minister to Riyadh.

The Israeli military said it killed two Palestinian gunmen who fired on troops in the occupied West Bank early on Wednesday, the latest in near-daily violence roiling the region.

The shooting came as tensions are at a fever pitch following a series of Israeli airstrikes in the Gaza Strip that killed three senior Islamic Jihad militants and 10 others — most of them women and children — on Tuesday. Palestinian militants have pledged to retaliate and Israel says it is prepared for a further escalation of hostilities.

Tunisian authorities were Wednesday investigating a shooting spree by a police officer that claimed five lives and sparked mass panic during a Jewish pilgrimage at Africa's oldest synagogue.

Security forces threw a tight cordon around the site on Djerba island as officials probed whether Tuesday's shootings were a random killing spree or an anti-Semitic terrorist attack.

The U.N. chief has expressed hope that Syria's return to the Arab League and its engagement with regional powers could spur progress in resolving the 13-year Syrian civil war, as Damascus faced pressure to be transparent about chemical weapons.

Secretary-General Antonio Guterres said he believes the region "has a vital role to play in the search for settlement of the conflict," which began with an uprising against President Bashar Assad's rule in 2011 that was met with a violent crackdown. The civil war has killed nearly a half million people, and displaced half the country's pre-war population of 23 million.