CAIRO — An Egyptian police officer was shot dead in a Nile Delta town on Thursday while trying to arrest suspects wanted in connection with a killing of a security official, the interior ministry said.

Captain Ahmed Samir came under fire during an early morning operation to arrest militants in the province of Qulubiya, the ministry said in a statement.

They were suspected of involvement in the shooting in Cairo on Sunday of Interior Ministry Lt. Col. Mohamed Mabruk.

Mabruk's killing deepened concerns that Egypt, a U.S. ally, could face an Islamist insurgency.

He was part of an Interior Ministry unit that closely tracks the Muslim Brotherhood, which won every election since a popular uprising toppled autocrat Hosni Mubarak in 2011.

One of the Brotherhood's leaders, Mohammed Morsi, was ousted as Egypt's president by the army in July. Since then, attacks by Islamists based in the Sinai Peninsula near Israel have risen sharply.

Islamist militants have also attacked police officials in Cairo and elsewhere.

State-run newspaper Al-Ahram quoted a forensics specialist as saying that Samir died from a bullet wound to his neck, and that he was shot at a range of no more than five meters.

A Sinai-based militant group, Ansar Bayt al-Maqdis, claimed responsibility for the killing of Mabruk, who security officials say was supposed to be a witness in one of several legal cases against Morsi, who is on trial for inciting violence.

The army-backed government does not distinguish between the Brotherhood and al Qaida-inspired militants in Sinai, who attack security forces almost daily.

A suicide car bombing killed at least 10 Egyptian soldiers in the Sinai on Wednesday, one of the deadliest attacks there since militants stepped up violence after Morsi's overthrow.

Militant violence, together with political tension between the Brotherhood and the government, is weighing on investment and tourism in Egypt, which has a peace treaty with Israel and contains the strategic Suez Canal.