Babel unexpected token compiling react component

I'm trying to compile the following code using babel but it's giving me an "unexpected token" on the character "=" on the following line:

state = {};

Babel version is: 6.24.1 (babel-core 6.25.0)

The code:

import {Button, Menu} from 'semantic-ui-react';

class AppBar extends Component {
    state = {};

    handleItemClick = (e, { name }) => this.setState({ activeItem: name });

    render() {
        const { activeItem } = this.state;

        return (
            <Menu>
                <Menu.Item
                    name='dashboard'
                    active={activeItem === 'dashboard'}
                    onClick={this.handleItemClick}
                >
                    Dashboard
                </Menu.Item>

                <Menu.Item
                    name='contacts'
                    active={activeItem === 'contacts'}
                    onClick={this.handleItemClick}
                >
                    Contact Lists
                </Menu.Item>

                <Menu.Item
                    name='messages'
                    active={activeItem === 'messages'}
                    onClick={this.handleItemClick}
                >
                    Messages
                </Menu.Item>
            </Menu>
        )
    }
}

ReactDOM.render(
  <AppBar/>,
  document.getElementById('root')
);

I'm using the es2015 and react presets.

What is the problem? Thanks.