CAIRO — Islamists appear to have taken a strong majority of seats in the first round of Egypt’s first parliamentary vote since Hosni Mubarak’s ouster, a trend that if confirmed would give religious parties a popular mandate in the struggle to win control from the ruling military and ultimately reshape a key U.S. ally.

Final results, expected Friday, will be the clearest indication in decades of Egyptians’ true political views and give the long-banned Muslim Brotherhood a major role in the country’s first freely elected parliament. An Islamist majority could also herald a greater role for conservative Islam in Egyptian social life and shifts in foreign policy, especially toward Israel and the Palestinians.

Judges overseeing the Egyptian vote count said Thursday that near-complete results show the Muslim Brotherhood, the country’s largest and best organized political group, could take as many as 45 percent of the contested seats.

In addition to the Muslim Brotherhood wins, parties backed by ultraconservative Salafist Muslims looked poised to take 20 percent, giving Islamist parties a striking majority in the first round of voting.

The Islamist victories came at the expense of a coalition of liberal parties called the Egyptian block, the group most closely linked to the youth activists who launched the anti-Mubarak uprising — and which is expected to win only about 20 percent of seats.