PARIS, April 22 (Reuters) - French infrastructure group Vinci posted on Thursday a 5% rise in first-quarter sales, helped by a rebound of its construction business even as its airport arm, which includes London's Gatwick, suffered from the COVID-19 crisis.

The company, which also operates in the energy sector and saw activity pick up there, was hit hard last year by coronavirus lockdowns worldwide that paralysed real estate and construction projects, its biggest source of earnings.

These have now restarted, in spite of enduring COVID-19 restrictions in places like its French home market, helping Vinci revenues reach 10.2 billion euros ($12.26 billion) in the three months to March.

The group announced earlier in April that it was buying the energy business of Spain's ACS for about 4.9 billion euros, as it makes a push into areas such as renewables projects and contracting in the power sector.

International travel remains muted, and revenue from Vinci's airports unit was down 70% year on year in the quarter, although the group said there were some improvements since March in the United States and regions were restrictions are easing.

Its highways division also posted falling sales.

($1 = 0.8322 euros) (Reporting by Sarah White; Editing by Edmund Blair)