JERUSALEM — Palestinian militants from Gaza fired dozens of rockets and mortar shells into southern Israel overnight Tuesday and into Wednesday morning, critically wounding two Thai workers in an Israeli border community, Israeli authorities said. Four Palestinian militants in rocket-launching squads were killed in Israeli airstrikes, according to Palestinian officials.

The surge in cross-border violence came hours after a landmark visit to Gaza by the emir of Qatar, Sheik Hamad bin Khalifa al-Thani, who pledged $400 million for projects there. It also came as a major American-Israeli joint military exercise was underway in Israel, underlining the volatility and potential for escalation in the area at a delicate time before the US elections in November and Israeli elections scheduled for January.