Israel's Counter-Terrorism Bureau on Thursday issued a travel warning for Israelis planning to visit Sri Lanka, saying there was a “high and concrete” chance of a terror attack.The Bureau has set a Level 2 travel warning, which is the second highest warning.This comes just days after the Easter Sunday nine suicide bombings that killed 359 people and injured over 500 across the country.The agency stressed that Israeli travelers still in Sri Lanka should leave the island at the soonest possible time, and also advised those planning trips to cancel.The decision to issue the warning was made after consultations with security officials and the Foreign Ministry.The Sri Lankan authorities on Thursday ordered the country's religious leaders to keep all Catholic churches closed and not to hold prayer services until security improves, a senior priest told AFP. "There will be no public masses until further notice," the priest told the News Agency. Sri Lankan citizens continue to face warnings of suspicious objects and roadblocks, Meanwhile, also on Thursday, Sri Lankan police locked down the central bank, and the road leading to the capital's main airport was shut briefly by a bomb scare as more people were swept up in the search for those behind the terrorist attacks.More people, including foreigners, were also detained for questioning overnight as domestic and international authorities probed deeper into the bombings, which were potentially the deadliest operation claimed by Islamic State.Local police said an Egyptian and several Pakistanis were among those detained overnight on Thursday, although there was no immediate suggestion they had direct links to the attacks.Most of the Easter Sunday victims were Sri Lankans, although authorities confirmed at least 38 foreigners were also killed. These included British, US, Australian, Turkish, Indian, Chinese, Danish, Dutch and Portuguese nationals.The bombings shattered the relative calm that has existed in Buddhist-majority Sri Lanka since a civil war against mostly Hindu, ethnic Tamil separatists ended 10 years ago, and raised fears of a return to sectarian violence.Sri Lanka's 22 million people include minority Christians, Muslims and Hindus. Until now, Christians had largely managed to avoid the worst of the island's conflict and communal tensions.